Few more notes from customers:

The only obvious pattern is that it won't let users sign in to devices that they haven't previously signed into. They can still sign in on devices that they have previously signed into. I have powerwashed the device and we are still having the same issue, except that now no-one can log in to it.

It also does not seem to be network related as issue occurs on tethered device also.

I am adding debug log and video shared by customer in case# 17957791
https://drive.google.com/open?id=1PULOSxsjJSFdn9i4oHvf1TmWMvij8Sxr
They have a bit different behavior, it looks like Chrome just crashes completely on the login:

2019-01-08T11:32:06.487980+00:00 WARNING kernel: [  173.704304] do_trap: 9 callbacks suppressed
2019-01-08T11:32:06.488012+00:00 INFO kernel: [  173.704321] traps: chrome[3498] trap int3 ip:59246e528ea8 sp:7ffe43338ac0 error:0
2019-01-08T11:32:06.507428+00:00 INFO crash_reporter[4519]: libminijail[4519]: mount /dev/log -> /dev/log type ''
2019-01-08T11:32:06.509977+00:00 DEBUG kernel: [  173.726765] SELinux: initialized (dev tmpfs, type tmpfs), uses transition SIDs
2019-01-08T11:32:06.517989+00:00 DEBUG kernel: [  173.734207] SELinux: initialized (dev tmpfs, type tmpfs), uses transition SIDs
2019-01-08T11:32:06.524722+00:00 WARNING crash_reporter[4519]: [user] Received crash notification for chrome[3498] sig 5, user 1000 (ignoring call by kernel - chrome crash; waiting for chrome to call us directly)
2019-01-08T11:32:06.525189+00:00 WARNING crash_reporter[4519]: [ARC] Received crash notification for chrome[3498] sig 5, user 1000 (ignoring - crash origin is not ARC)
2019-01-08T11:32:06.766253+00:00 INFO session_manager[3478]: [INFO:session_manager_service.cc(297)] Browser process 3498 exited with signal 5 (Trace/breakpoint trap)


Roll back to v.69 does not help.   

vkasatkin: those logs seem to be from a Neverware CloudReady device running 63...

Are customers getting "Sign-in error. Chrome OS could not sync your data because your account sign-in details are out of date" notification if they are able to login? 
Trying to understand if it's the same issue or not.

jayhlee@ - yes, there are two set of debug logs they shared with us. 
One is from  Dell Chromebook 11 3189 (Kefka) and second from their CloudReady device, which they also tried.
I have moved CloudReady device logs to avoid confusion 

[8466:8466:0108/165556.810440:ERROR:user_cloud_policy_manager_chromeos.cc(677)] Policy fetch failed for the user. Aborting profile initialization
[8466:8466:0108/165556.813307:ERROR:user_cloud_policy_manager_chromeos.cc(677)] Policy fetch failed for the user. Aborting profile initialization

that seems to be in all the UI log files of all of these. Think we may have policy server issues...

filed b/122532046 as this seems to be server-side (various client versions seeing same error).

This appears to have been a server-side issue per #9; can functionality be confirmed and if so, close the bug?

marking as closed as server side bug is confirmed fixed and issue does not seem to have been client-side.