NetXMS Support Forum

Version = 3.9.178
Windows Server 2019
Postgres Db backend

Receiving these on NetXMS core server - it does appear the watchdog has restarted in every occurrence.

Alarm
Thread "Poll Manager" is not responding

and server.log entries?
2021.09.06 19:28:28.406 *E* [watchdog           ] Thread "Poll Manager" does not respond to watchdog thread
2021.09.06 19:28:28.421 *I* [watchdog           ] Thread "Poll Manager" returned to running state

Watchdog process is checking if all threads are running by communicating with them. There is some timeout, if watchdog does not receive reply within that timeout, these events are generated. In this case after 15 milliseconds after the error was generated watchdog received reply from the thread which resolved the error.
This could be if there's high CPU and/or RAM usage on the system. Check monitoring data on CPU and RAM consumption on your server.