We did not add support for the OS version you referenced (Ubu 16.04) until late spring with version 5.3.1 (for the base AD client).
adbindd relies on the base agent. If there were issues with the older agent and they were corrected with the newer one they may or may not have to do with the problem you described.
We ruled-out version inconsistency, let's see if the problems happen again, if not, then we'll have to do further troubleshooting.