Hi Sarah,

Apologies for the delay on this one.

It looks like your issue is related to the fix in 2.2.21 and is due to assignment records not being properly cleared up when users are unassigned, so the code is attempting to remove an exception that doesn't really exist.

I'd recommend an upgrade to 2.2.23 as both 2.2.21 and 2.2.23 contain fixes in this area. 2.2.23 also contains various Security fixes for both Totara and Moodle so you are probably best to upgrade to at least that point anyway - the latest 2.2 is 2.2.26.

Hope that helps,

Ciaran