Compression gets started and runs out-of-memory although NOT selected

Installation details:

• Nextcloud Docker container: official community edition
• Nextcloud version: 23.0.2
• Backup version: 1.0.6
• Backup to external storage

an nfs volume is mounted to the server and mapped into the container:
xxx.yyy.com:/gdx_dr_backup_1 1.0T 362G 663G 36% /var/nextcloud/nxtcld/backup

 app:
    image: nextcloud:23
    restart: unless-stopped
    volumes:
      - /var/nextcloud/nxtcld/html:/var/www/html
      - /var/nextcloud/nxtcld/config:/var/www/html/config
      - /var/nextcloud/nxtcld/data:/var/www/html/data
      - /var/nextcloud/nxtcld/backup:/var/www/html/backup
    environment:

www-data@56f419615897:~/html$ php occ backup:external:list
+-----------+--------------------------------------+------------------+
| StorageId | Path                                 | Storage Folder   |
+-----------+--------------------------------------+------------------+
| 388       | local::/var/www/html/backup/rpoints/ | restoring_points |
+-----------+--------------------------------------+------------------+
www-data@56f419615897:~/html$ php occ backup:external:appdata
Your appdata is currently on an external storage:
Storage Id: 389
Storage: local::/var/www/html/backup/tmpdata/
Root: app_data

www-data@56f419615897:~/html$

• Compression is NOT selected (but was once, then disabled)

following error message gets generated and system remains in maintenance mode:

PHP Fatal error: Allowed memory size of 536870912 bytes exhausted (tried to allocate 1052672 bytes) in /var/www/html/3rdparty/deepdiver/zipstreamer/src/ZipStreamer.php on line 359

Start with 3rdparty/deepdiver/zipstreamer/src/ZipStreamer.php at line 359 and review the backup compression path and the reported backup:external:list and backup:external:appdata configuration. Reproduce the backup with compression disabled using the shown external-storage setup, then verify that compression does not run, memory is not exhausted, and the system does not remain in maintenance mode.