Dear @William
Thank you a lot for this nice answer and explanations.
We did update and harmonise the ntp server of all 8 FreeIPA servers that we have and
continued to see a lot of these errors above over the next couple weeks.
However, since 10 days ago, all messages of this sort stopped and have not yet returned.
Is there some catch up mechanism that somehow was able to "heal" ?
Thanks a lot for your insights,
Christophe