Details, of course!
We upgraded one minor at a time, starting the servers and letting them run for 10-15 minutes.
Yes, the errors started occuring after the bump (as far as I can tell, I’m looking back at logs here).
Looking at the History node log, there where a lot of “Error updating ack level for shard”, “Error updating timer ack level for shard” & “Critical attempts processing workflow task”-warnings. Perhaps not related.
We don´t have any schedules, so I ran the Elasticsearch upgrade script after updating.
We use the secondary Elasticsearch index as well, and it was not updated with the custom search attributes (tctl add search attribute does not touch it), so we added those in manually afterwards as well.