Shared Calendar Events not Visible

My wife and I use Nextcloud for our calendars and task (among other things). Recently (in the last 3 months) some of our shared calendars started misbehaving. They aren’t showing the same events on either side of the share.

I have tried un-sharing and re-sharing. When I add an event from either the sharee or the to shared the even doesn’t show up on the other. What do I need to do to fix that?

As another oddity to this the shared task list still works.

I am running AIO on UnRaid. I did have to restore from a backup a few months ago when my server started acting up.

Anyone have any suggestions?