We have discovered that we cannot add new activities to our courses. Open up a course and click on the Add an activity or resource link on the page. Add the activity/resource as normal. Clicking either the Save and return to course or the Save and display buttons will send us to the Main Menu page. The activity is saved to the Main Menu block instead of the course itself. When we view the Main Menu block in edit mode we only see one activity. Opening the activity gives us the option to view the next activity. This button allows us to see several new activities that have been incorrectly added but no way to remove them.

How can we remove activities in the Main Menu block if they aren't displayed on the block itself?

Is there a course menu block that has gone missing from our classes? If so, how do we get it back?

All of our courses seem to be affected. We have duplicated this issue using an account with Manager/Course Creator system privileges as well as a site admin account. We tried switching to the default theme and produced the same results. This seems to have started after loading the Moodle 3.11.5+ (Build: 20220218) update. How can we resolve this issue?