@Dennis ... before the 3.11.5 release .. please see:
https://docs.moodle.org/dev/Releases#Moodle_3.11
General release calendar - where is says:
Minor (Point) (eg. 3.x.y) 2 monthly Second Monday of July, September, November, March and May.
Third Monday of January.
Assuming your academic calendar begins new courses after the new year - 1st week of Jan? am gonna guess the fix might not come before you need it.
Thus, that leaves only 2 options .. neither recommended ..
1. Make a .mbz backup and doctor the un-compressed backup then re-compress and restore. That's if one can ID what to fix.
2. Alter related DB tables directly ... again, only if one can ID the problem.
The PM I sent you on this system kinda offers that (at least to investigate - no fee - ... only with my 3.11.4+ sandbox server.
'SoS', Ken