I ran into the course restore error, "The backup file contains more than one top-level question categories for context XXX." I did a Moodle forum search & found this thread: https://moodle.org/mod/forum/discuss.php?d=390207
At the end of the thread, there's a suggestion, "Try to take a backup without filters being selected. It should work as it has for me."
Just to confirm, I tried it & it worked for me too - I just deselected filters in the course backup process
- Moodle 3.10
- VPS LAMP stack
- VPS 4GB, 2 cores, Ubuntu 20.04 LTS
- Apache, MySQL, & PHP all latest versions as of Jan 2021
- MySQL & PHP settings optimised for server (shouldn't be problems with max packet size, process timeouts, etc.)
Couldn't find a specific report in the Moodle Tracker for this bug.