Wild guess: The problem may be that some of the commits in the merge have a Change-Id.

I see this now even with non-merge uploads and with uploads which previously caused no problems. If it happens with non-merges, the push is simply rejected and there is no CL. If it happens with merges, the CL still shows up.
Error message is always similar to the following.

remote: Resolving deltas: 100% (55/55)
remote: Processing changes: new: 1, done    
To https://chromium.googlesource.com/chromiumos/third_party/kernel
 ! [remote rejected]           merge/chromeos-4.14-v4.14.14 -> refs/for/chromeos-4.14/merge-v4.14.14 (internal error)
error: failed to push some refs to 'https://chromium.googlesource.com/chromiumos/third_party/kernel'

Are you getting this with branch changes that have Change-ID, or not?

Not really clear what is triggering the problem; it does not seem to be related to Change-IDs after all. Yesterday I was able to push a branch where some patches include a Change-ID.

I saw this problem when trying to upload 3 very simple changes.  Specifically when I uploaded the 3 patches ending at:
  https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/869417

I got an error message when trying to upload.  I then rebased these patches and added a few more atop and uploaded again and it worked.

Besides being confusing, the end result was that there are now more than one patch with the same Change ID in the same repo/branch.  See:
  https://chromium-review.googlesource.com/q/I50627c4ee1e1c1c0168c2ca74f763d80ab0d42f5

I thought that was supposed to be impossible, but apparently gerrit is confused?

I saw "internal error" on Friday when pushing a set of cherry-picks which all had Change-id's from previous commits. The CLs appeared to all be created and I added one more change that I overlooked before. repo upload completed with no issues when I uploaded again.

Output below is from the first attempt to upload which claimed it failed.

(cr) (update_r8152-3.14) grundler@firesword ~/trunk/src/third_party/kernel/v3.14 $ repo upload --br=update_r8152-3.14 -t --no-verify
Upload project src/third_party/kernel/v3.14/ to remote branch refs/heads/chromeos-3.14:
  branch update_r8152-3.14 (55 commits, Sun Jan 14 21:42:50 2018 -0800):
         b1f13f4c UPSTREAM: r8152: Fix error path in open function
         ee8b321e UPSTREAM: r8152: split rtl8152_suspend function
         fda7a799 UPSTREAM: r8152: fix rx issue for runtime suspend
         587d4a03 UPSTREAM: r8152: fix the sw rx checksum is unavailable
         c4502a0b UPSTREAM: r8152: don't execute runtime suspend if the tx is not empty
         09b75ad0 UPSTREAM: r8152: Remove unused function usb_ocp_read()
         1616ede2 UPSTREAM: r8152: re-schedule napi for tx
         badafcb1 UPSTREAM: r8152: fix rtl8152_post_reset function
         2bf3715c UPSTREAM: r8152: avoid start_xmit to schedule napi when napi is disabled
         3b33e5e5 UPSTREAM: r8152: prevent the driver from transmitting packets with carrier off
         4f72a2f6 UPSTREAM: r8152: move the settings of PHY to a work queue
         dc3684dc UPSTREAM: r8152: move the setting for the default speed
         f34916d4 UPSTREAM: r8152: save the speed
         39ba89fa UPSTREAM: r8152: disable MAC clock speed down
         f32a7e2b UPSTREAM: r8152: reset the bmu
         f293999f UPSTREAM: r8152: correct the rx early size
         eebb64c3 UPSTREAM: r8152: modify the check of the flag of PHY_RESET in set_speed function
         4f51fc96 UPSTREAM: r8152: clear LINK_OFF_WAKE_EN after autoresume
         f4d48b71 UPSTREAM: r8152: fix runtime function for RTL8152
         8789fc63 UPSTREAM: r8152: remove rtl_phy_reset function
         7093eed2 UPSTREAM: r8152: remove cancel_delayed_work_sync in rtl8152_set_speed
         a3b929b1 UPSTREAM: r8152: move some functions
         324cdb73 UPSTREAM: r8152: move enabling PHY
         b9aa88ed UPSTREAM: r8152: move PHY settings to hw_phy_cfg
         eee6a9aa UPSTREAM: r8152: remove r8153_enable_eee
         04b80888 UPSTREAM: r8152: disable ALDPS and EEE before setting PHY
         4eee60f7 UPSTREAM: r8152: fix the wrong spelling
         2ccfdd71 UPSTREAM: r8152: avoid start_xmit to call napi_schedule during autosuspend
         f733f91a UPSTREAM: r8152: check rx after napi is enabled
         7e9458bd UPSTREAM: r8152: simply the arguments
         7a01c5c7 UPSTREAM: r8152: fix the list rx_done may be used without initialization
         6fc36e36 Revert "CHROMIUM: r8152: add support for version 0x6010"
         6fe9887e UPSTREAM: r8152: check hw version first
         89a01868 UPSTREAM: r8152: set the RMS of RTL8153 according to the mtu
         83eae099 UPSTREAM: r8152: fix the rx early size of RTL8153
         1edbf742 UPSTREAM: r8152: The Microsoft Surface docks also use R8152 v2
         a03cde3d UPSTREAM: r8152: add r8153_phy_status function
         1421d8ab UPSTREAM: r8152: adjust lpm settings for RTL8153
         f7a0ad7c UPSTREAM: r8152: adjust the settings about MAC clock speed down for RTL8153
         dd5c2c5f UPSTREAM: r8152: move the setting of rx aggregation
         0290f2d0 UPSTREAM: r8152: adjust rtl8153_runtime_enable function
         424a00c9 UPSTREAM: r8152: adjust U2P3 for RTL8153
         e0b90c9e UPSTREAM: r8152: move the default coalesce setting for RTL8153
         9de85d51 UPSTREAM: r8152: move the initialization to reset_resume function
         84bc2552 UPSTREAM: r8152: check if disabling ALDPS is finished
         75381e69 UPSTREAM: r8152: avoid rx queue more than 1000 packets
         88c4d354 UPSTREAM: r8152: give the device version
         d0d99cd7 UPSTREAM: r8152: support new chip 8050
         e42f70e0 UPSTREAM: r8152: support RTL8153B
         d2a998cb UPSTREAM: r8152: add byte_enable for ocp_read_word function
         5a9c4641 UPSTREAM: r8152: split rtl8152_resume function
         ef7d07b3 UPSTREAM: r8152: move calling delay_autosuspend function
         05b84b24 UPSTREAM: r8152: correct the definition
         d895deb4 UPSTREAM: net: usb: r8152: constify usb_device_id
         9c2e74bb UPSTREAM: drivers/net/usb: add device id for TP-LINK UE300 USB 3.0 Ethernet
to https://chromium-review.googlesource.com (y/N)? y
ATTENTION: You are uploading an unusually high number of commits.
YOU PROBABLY DO NOT MEAN TO DO THIS. (Did you rebase across branches?)
If you are sure you intend to do this, type 'yes': yes
remote: Processing changes: new: 55, done            
remote: (W) 587d4a0: commit subject >50 characters; use shorter first paragraph        
remote: (W) c4502a0: commit subject >50 characters; use shorter first paragraph        
remote: (W) 09b75ad: commit subject >50 characters; use shorter first paragraph        
remote: (W) 2bf3715: commit subject >50 characters; use shorter first paragraph        
remote: (W) 3b33e5e: commit subject >50 characters; use shorter first paragraph        
remote: (W) 4f72a2f: commit subject >50 characters; use shorter first paragraph        
remote: (W) dc3684d: commit subject >50 characters; use shorter first paragraph        
remote: (W) eebb64c: commit subject >50 characters; use shorter first paragraph        
remote: (W) 4f51fc9: commit subject >50 characters; use shorter first paragraph        
remote: (W) 7093eed: commit subject >50 characters; use shorter first paragraph        
remote: (W) 04b8088: commit subject >50 characters; use shorter first paragraph        
remote: (W) 2ccfdd7: commit subject >50 characters; use shorter first paragraph        
remote: (W) 7a01c5c: commit subject >50 characters; use shorter first paragraph        
remote: (W) 6fc36e3: commit subject >50 characters; use shorter first paragraph        
remote: (W) 89a0186: commit subject >50 characters; use shorter first paragraph        
remote: (W) 1edbf74: commit subject >50 characters; use shorter first paragraph        
remote: (W) f7a0ad7: commit subject >50 characters; use shorter first paragraph        
remote: (W) dd5c2c5: commit subject >50 characters; use shorter first paragraph        
remote: (W) 0290f2d: commit subject >50 characters; use shorter first paragraph        
remote: (W) e0b90c9: commit subject >50 characters; use shorter first paragraph        
remote: (W) 9de85d5: commit subject >50 characters; use shorter first paragraph        
remote: (W) 84bc255: commit subject >50 characters; use shorter first paragraph        
remote: (W) 75381e6: commit subject >50 characters; use shorter first paragraph        
remote: (W) d2a998c: commit subject >50 characters; use shorter first paragraph        
remote: (W) ef7d07b: commit subject >50 characters; use shorter first paragraph        
remote: (W) 9c2e74b: commit subject >50 characters; use shorter first paragraph        
remote: 
remote: New Changes:        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876804 UPSTREAM: r8152: Fix error path in open function        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876805 UPSTREAM: r8152: split rtl8152_suspend function        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876806 UPSTREAM: r8152: fix rx issue for runtime suspend        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876807 UPSTREAM: r8152: fix the sw rx checksum is unavailable        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876808 UPSTREAM: r8152: don't execute runtime suspend if the tx is not empty        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876809 UPSTREAM: r8152: Remove unused function usb_ocp_read()        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876810 UPSTREAM: r8152: re-schedule napi for tx        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876811 UPSTREAM: r8152: fix rtl8152_post_reset function        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876812 UPSTREAM: r8152: avoid start_xmit to schedule napi when napi is disabled        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876813 UPSTREAM: r8152: prevent the driver from transmitting packets with carrier off        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876814 UPSTREAM: r8152: move the settings of PHY to a work queue        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876815 UPSTREAM: r8152: move the setting for the default speed        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876816 UPSTREAM: r8152: save the speed        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876817 UPSTREAM: r8152: disable MAC clock speed down        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876818 UPSTREAM: r8152: reset the bmu        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876819 UPSTREAM: r8152: correct the rx early size        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876820 UPSTREAM: r8152: modify the check of the flag of PHY_RESET in set_speed function        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876821 UPSTREAM: r8152: clear LINK_OFF_WAKE_EN after autoresume        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876842 UPSTREAM: r8152: fix runtime function for RTL8152        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876843 UPSTREAM: r8152: remove rtl_phy_reset function        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876844 UPSTREAM: r8152: remove cancel_delayed_work_sync in rtl8152_set_speed        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876845 UPSTREAM: r8152: move some functions        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876846 UPSTREAM: r8152: move enabling PHY        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876847 UPSTREAM: r8152: move PHY settings to hw_phy_cfg        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876848 UPSTREAM: r8152: remove r8153_enable_eee        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876849 UPSTREAM: r8152: disable ALDPS and EEE before setting PHY        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876850 UPSTREAM: r8152: fix the wrong spelling        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876851 UPSTREAM: r8152: avoid start_xmit to call napi_schedule during autosuspend        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876852 UPSTREAM: r8152: check rx after napi is enabled        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876853 UPSTREAM: r8152: simply the arguments        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876854 UPSTREAM: r8152: fix the list rx_done may be used without initialization        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876855 Revert "CHROMIUM: r8152: add support for version 0x6010"        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876856 UPSTREAM: r8152: check hw version first        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876857 UPSTREAM: r8152: set the RMS of RTL8153 according to the mtu        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876858 UPSTREAM: r8152: fix the rx early size of RTL8153        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876859 UPSTREAM: r8152: The Microsoft Surface docks also use R8152 v2        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876860 UPSTREAM: r8152: add r8153_phy_status function        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876861 UPSTREAM: r8152: adjust lpm settings for RTL8153        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876862 UPSTREAM: r8152: adjust the settings about MAC clock speed down for RTL8153        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876863 UPSTREAM: r8152: move the setting of rx aggregation        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876864 UPSTREAM: r8152: adjust rtl8153_runtime_enable function        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876865 UPSTREAM: r8152: adjust U2P3 for RTL8153        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876866 UPSTREAM: r8152: move the default coalesce setting for RTL8153        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876867 UPSTREAM: r8152: move the initialization to reset_resume function        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876868 UPSTREAM: r8152: check if disabling ALDPS is finished        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876869 UPSTREAM: r8152: avoid rx queue more than 1000 packets        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876870 UPSTREAM: r8152: give the device version        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876871 UPSTREAM: r8152: support new chip 8050        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876872 UPSTREAM: r8152: support RTL8153B        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876873 UPSTREAM: r8152: add byte_enable for ocp_read_word function        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876874 UPSTREAM: r8152: split rtl8152_resume function        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876875 UPSTREAM: r8152: move calling delay_autosuspend function        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876876 UPSTREAM: r8152: correct the definition        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876877 UPSTREAM: net: usb: r8152: constify usb_device_id        
remote:   https://chromium-review.googlesource.com/#/c/chromiumos/third_party/kernel/+/876878 UPSTREAM: drivers/net/usb: add device id for TP-LINK UE300 USB 3.0 Ethernet        
remote: 
To https://chromium-review.googlesource.com/chromiumos/third_party/kernel
 ! [remote rejected]           update_r8152-3.14 -> refs/for/chromeos-3.14/update_r8152-3.14 (internal server error: Error inserting change/patchset)
error: failed to push some refs to 'https://chromium-review.googlesource.com/chromiumos/third_party/kernel'

----------------------------------------------------------------------
[FAILED] src/third_party/kernel/v3.14/ update_r8152-3.14 (Upload failed)

(cr) (update_r8152-3.14) grundler@firesword ~/trunk/src/third_party/kernel/v3.14 $ 

I encountered the same error and it finally worked after few tries.

error: failed to push some refs to 'https://chrome-internal-review.googlesource.com/chromeos/autotest-cheets'

There's nothing that I can do about Gerrit return "Internal server error", the equivalent of a 500. Please file these bugs using either the "Send Feedback" button at the bottom of a Gerrit page, or using go/gob-ticket.