Please apologise for the crude form in which I'm going to explain this.
I promise I will try to add reproduction steps.

WHAT YOU EXPECT:
Moodle deals with all this silently.

WHAT ACTUALLY HAPPENS
It is that in our previous 3.10, due to a discontinuation of a plugin, a whole activity was uninstalled (well, not fully. It was mod_kalvidpres.) which lead to course modules not being displayed any more which was fine, but their entries still present in the database. Moodle 3.10 handeled this without any flaw.

But upon updating to Moodle 3.11.2 this situation lead to Invalid course module ID errors (Error code: invalidcoursemodule) in some places for some users. In course pages (workaround: go to edit.php and turn off activity completion) but also in dashboard, all probably depending whether the course/the user's dashboard hit a context where an orphaned course module id was hit.

It would be nice to assure a more faulty tolerant way to deal with such situations.
Classify as bug or as improvement based on your own evaluation, please.

Best,
Luca