Investigating poor build health for Daisy reveals that it is often failing due to failed HWTest [Sanity]. Looking further into the logs, this is the error I'm seeing:

  provision     FAIL: Unhandled DevServerException: CrOS auto-update failed for host chromeos2-row4-rack7-host8: cmd=['ssh', '-p', '22', '-oConnectionAttempts=4', '-oUserKnownHostsFile=/dev/null', '-oProtocol=2', '-oConnectTimeout=30', '-oServerAliveCountMax=3', '-oStrictHostKeyChecking=no', '-oServerAliveInterval=10', '-oNumberOfPasswordPrompts=0', '-oIdentitiesOnly=yes', '-i', '/tmp/ssh-tmpd29RZh/testing_rsa', 'root@chromeos2-row4-rack7-host8', '--', '/postinst', '/dev/mmcblk0p3'], extra env={'LC_MESSAGES': 'C'}

Here are a couple log files:
https://uberchromegw.corp.google.com/i/chromeos_release/builders/daisy-release%20release-R59-9460.B/builds/25/steps/HWTest%20%5Bsanity%5D/logs/stdio

https://uberchromegw.corp.google.com/i/chromeos_release/builders/daisy-release%20release-R59-9460.B/builds/27/steps/HWTest%20%5Bsanity%5D/logs/stdio

Not yet sure if the problem is limited to daisy or that particular DUT (that DUT did have some passes, but 3 of the failures I saw were all on the same one).