Recyclebin ... is using the backup process to create a backup of what was deleted. Could be a module(s). Could be a course.
Suggest setting Recyclebin to lowest amount of time to retain.
And set it to also show all the time in course menu for now.
In a course where someone removed a module, clicking the Recyclebin link will list what has been deleted and will provide a link to send to trash. That takes care of deleted modules in course.
There is no recyclebin link when one deletes entire course or category containing multiple courses. Thus the setting for lowest time to retain.
Been through this recently with a site that was in dire need of clean up ... courses simply hidden ... many of those hadn't been used in 7 years! While courses had been reset - removing users and any assignment submissions, etc. there were still course backups (multiple) that a teacher made retained. Had to do the tweaks to Recyclebin settings to get the job done.
This massive clean up also necessitated a few tables in the DB to be optimized ... to regain space used by those tables.
'SoS', Ken