Although not always, it happens more and more frequently recently.

$ cros flash chromeos6-row2-rack12-host10.cros xbuddy://remote/squawks/latest-stable

17:09:35: NOTICE: Preparing to update the remote device chromeos6-row2-rack12-host10.cros
17:09:47: NOTICE: Using image squawks-release/R68-10718.93.0/chromiumos_test_image.bin
17:24:52: ERROR: Cannot connect to devserver (timed out)
17:24:53: WARNING: --- Start output from /usr/local/google/crostc/chromeos/chroot/tmp/devserver_wrapper08gQ6F/dev_server.log ---[23/Aug/2018:17:09:49] DEVSERVER Using cache directory /mnt/host/source/devserver/static/cache
[23/Aug/2018:17:09:49] DEVSERVER Serving from /mnt/host/source/devserver/static
[23/Aug/2018:17:09:49] XBUDDY Using shadow config file stored at /mnt/host/source/src/platform/dev/shadow_xbuddy_config.ini
[23/Aug/2018:17:09:49] ENGINE Listening for SIGHUP.
[23/Aug/2018:17:09:49] ENGINE Listening for SIGTERM.
[23/Aug/2018:17:09:49] ENGINE Listening for SIGUSR1.
[23/Aug/2018:17:09:49] ENGINE Bus STARTING
[23/Aug/2018:17:09:49] ENGINE Started monitor thread '_TimeoutMonitor'.
[23/Aug/2018:17:09:49] ENGINE PID 36927 written to '/tmp/devserver_wrapper08gQ6F/devserver_wrapperUFHVW1'.
[23/Aug/2018:17:09:49] ENGINE (wait_for_free_port) No cached port to wait for.
[23/Aug/2018:17:09:49] ENGINE (wait_for_occupied_port) Waiting for actual port 44155.
[23/Aug/2018:17:09:49] ENGINE Port 44155 written to '/tmp/devserver_wrapper08gQ6F/dev_server.port'.
[23/Aug/2018:17:09:49] ENGINE Serving on :::0
[23/Aug/2018:17:09:49] ENGINE Bus STARTED
::ffff:127.0.0.1 - - [23/Aug/2018:17:09:52] "GET /check_health HTTP/1.1" 200 371 "" "Python-urllib/2.7"
[23/Aug/2018:17:09:52] XBUDDY Cannot find /mnt/host/source/src/build/images; skip syncing image registry.
[23/Aug/2018:17:09:52] XBUDDY Path is remote/squawks-release/R68-10718.93.0/test, location suffix is -release
[23/Aug/2018:17:09:52] XBUDDY Get artifact 'test' with board squawks-release and version R68-10718.93.0'. Locally? False
[23/Aug/2018:17:09:58] XBUDDY Resolved version R68-10718.93.0 to squawks-release/R68-10718.93.0.
[23/Aug/2018:17:09:58] XBUDDY Returning path to payload: squawks-release/R68-10718.93.0/chromiumos_test_image.bin
[23/Aug/2018:17:09:58] XBUDDY Downloading ['full_payload', 'stateful'] from gs://chromeos-image-archive/squawks-release/R68-10718.93.0
[23/Aug/2018:17:09:58] GOOGLE_STORAGE_DOWNLOADER Downloading artifacts *_full_*->/mnt/host/source/devserver/static/squawks-release/R68-10718.93.0 stateful.tgz->/mnt/host/source/devserver/static/squawks-release/R68-10718.93.0.
[23/Aug/2018:17:09:58] A_U_TEST_PAYLOAD No marker file, *_full_*->/mnt/host/source/devserver/static/squawks-release/R68-10718.93.0 is not staged.
[23/Aug/2018:17:10:00] A_U_TEST_PAYLOAD Downloading file chromeos_R68-10718.93.0_squawks_full_dev.bin
--- End output from /usr/local/google/crostc/chromeos/chroot/tmp/devserver_wrapper08gQ6F/dev_server.log ---
17:25:03: WARNING: Devserver is unstoppable. Killing with SIGKILL
17:25:04: ERROR: Device update failed.
17:25:04: ERROR: cros flash failed before completing.
17:25:04: ERROR: timed out
17:25:04: ERROR: (Re-run with --debug for more details.)