Still confusing ...
With CLI backup you do have control over where the .mbz file is eventually copied to. With GUI you don't. IF not to the sea of files in moodledata/filedir/ could be going to priviate files ... your account (which is still in the sea of files - moodledata/filedir/xx/yy/longcontenthashname (note that's not humanly recognizable if one were to attempt to find that file.
From what you've shared this time, It has to do with a quiz and a plugin for quizzes.
There is a line: Unknown setting: questionbank
And the killer:
PHP Fatal error: restore_qtype_combined_plugin::convert_backup_to_questiondata()
https://moodle.org/plugins/qtype_combined
https://github.com/moodleou/moodle-qtype_combined/issues
How large is the first .mbz file?
When you make the backup of the 329 course via GUI, step through the screens and select 1/2 of the course to be included. Change the name the backup by adding '1sthalf' just after the 329 in the name. That should go to your private files. Then do a second backup, this time selecting the other half - adding to the name '2ndhalf' after the 329.
If you can id the quizzes that have qtype_combined in them you could attempt to exclude those quizzes from the backup.
On the restore ... new course for 1sthalf and if that restores, then restore 2ndhalf to same course.
Still might error ... but splitting the backup in 1/2 you then can look at the individual quiz's in that half.
Your cron job has a task that cleans up moodledata/temp/backup area. Check the task list for the frequency that runs ... could be that task is attempting to clean up the stuff you are trying to restore.
'SoS', Ken