Yesterday I applied the 2.5.2 update of MariaDB (which took around 20 minutes). All seemed well, but due to being distracted I didn’t check the logs at the time.
This morning I noticed that the values of all my helpers had reset themselves (which caused some of my automations to misfire).
The history for the helpers showed the values had changed more or less when the db upgrade was completed.
The db logs today show no errors, but HA has been restarted since the upgrade.
Of course, fixing the helper values is easy to do, but I thought I’d post here in case anyone else has the same issue.