Duplicate course not working --> restore not finishing

Hi community,

actually, I got problems duplicating courses. 

Enviroment details:

• I´m using Moodle 3.11.12, cloned from GitHub, using version control.
• Moodle is hosted inside AWS (Ubuntu 22.04), using Elastic File Storage for moodledata and Galera Cluster for MySQL as database backend 
• MySQL version 10.6.11 (max_allowed_packet  set to 256M)
• Apache 2.4.52, PHP 7.4 (max_input_vars = 5000)
• Moodle cron is running in CLI mode
• Debug messages are set to minimal

Issue:

After starting the copy process the process never finishes. It´s stuck while trying to restore the course. Inisde the mdl_backup_controller table I can see two entries, one for backup and one for restore. The backup entry got status 1000, the restore job remains in status 800. Inside my php log, I´ve found an entry "Potential coding error - existing temptables found when disposing database. Must be dropped!". I have also checked the entries inside the task logs and found two entries:

For the failed job following details are logged:

Execute adhoc task: core\task\asynchronous_copy_task
... started 08:37:07. Current memory use 49.5MB.
Course copy: Processing asynchronous course copy for course id: 3
Course copy: Backing up course, id: 3
Course copy: Restoring into course, id: 257
... used 179604 dbqueries
... used 210.54612398148 seconds
Adhoc task failed: core\task\asynchronous_copy_task,Der Datensatz kann nicht in der Datenbanktabelle course gefunden werden.

For the second job following details are logged:

Execute adhoc task: core\task\asynchronous_copy_task
... started 08:39:07. Current memory use 49.5MB.
Course copy: Processing asynchronous course copy for course id: 3
Course copy: Can not load backup controller for copy, marking job as failed
... used 353 dbqueries
... used 1.237398147583 seconds
Adhoc task complete: core\task\asynchronous_copy_task

I can also see that the backup folder inside moodledata/temp/backup ist created, the moodle_backup.xml is also present and seems valid. The .mbz is missing, but while watching the folder during the backup job, I can see that this file is being created (so I guess it has been already moved to another location?).  

What I´ve tried so far:

• Course backup using cli (admin/cli/backup.php --courseid=3 ) --> worked (size of .mbz: 47M )
• Course backup using webfrontend --> worked
• Purging cache
• Enable/Disable asynchronous backups
• Restoring backup using the webfrontend 

Any advice how to get this solved?