@StephenCWills , thanks for your answer!
Starting at the end: I tried unchecking Perform Timestamp Reasonability, but it had no effect.
Regarding the timestamp, my PMU (RPV311) is configured with UTC-3 (via IRIG-B), but in the reading carried out by the PMU Connection Tester it appears in UTC.
Could this be the cause of the problem? Is there a way to fix this?
I was replying in the other thread (How to Sync Time with PMU Device - #25 by ritchiecarroll) about this too.
Any ideas?