nyan-big-paladin has had a bunch of HWTest issues recently.

https://cros-goldeneye.corp.google.com/chromeos/healthmonitoring/buildDetails?buildbucketId=8924738436672788512
[Test-Logs]: graphics_Gbm_SERVER_JOB: FAIL: Aborting - unexpected final status message from client on chromeos4-row5-rack9-host17
[Test-History]: graphics_Gbm_SERVER_JOB
[Test-Logs]: graphics_Gbm_CLIENT_JOB.0: ABORT: Autotest client terminated unexpectedly: DUT is pingable, SSHable and did NOT restart un-expectedly. We probably lost connectivity during the test.

https://cros-goldeneye.corp.google.com/chromeos/healthmonitoring/buildDetails?buildbucketId=8924811486768777968
[Test-Logs]: graphics_Gbm: ERROR: Unhandled AssertionError: Unreasonably low CPU frequency.

https://cros-goldeneye.corp.google.com/chromeos/healthmonitoring/buildDetails?buildbucketId=8924839999139987296
[Test-Logs]: login_VMSanity_SERVER_JOB: FAIL: Aborting - unexpected final status message from client on chromeos4-row5-rack9-host19
[Test-History]: login_VMSanity_SERVER_JOB
[Test-Logs]: login_VMSanity_CLIENT_JOB.0: ABORT: Autotest client terminated unexpectedly: DUT is pingable, SSHable and did NOT restart un-expectedly. We probably lost connectivity during the test.
[Test-History]: login_VMSanity_CLIENT_JOB.0

At least 1 and 3 seem mildly related in terms of symptoms...

This looks like a common occurence on this board:
https://stainless.corp.google.com/search?view=list&first_date=2019-01-04&last_date=2019-01-10&board=%5Enyan%5C_big%24&status=FAIL&status=ERROR&status=ABORT&reason=.*client.*&exclude_cts=false&exclude_not_run=false&exclude_non_release=false&exclude_au=false&exclude_acts=false&exclude_retried=false&exclude_non_production=false