Old automated backup files are not deleted

Hi,

I noticed, that old automated backups are not deleted for a specific big course (9GB backup size).
Using Moodle v3.9.

I have on page
Site administration > Courses > Backups > Automated backup setup >
backup | backup_auto_active = ENABLED
backup | backup_auto_storage = Specified directory for automated backups
backup | backup_auto_destination = /dir/set
backup | backup_auto_max_kept = 2
backup | backup_auto_delete_days = 35 days
backup | backup_auto_min_kept = 2
backup | backup_auto_skip_hidden = DISABLED
backup | backup_auto_skip_modif_days = NEVER
backup | backup_auto_skip_modif_prev = DISABLED


But still the old backup files are not cleaned up:
moodle2-course-1636-20231105-0116.mbz
moodle2-course-1636-20231108-0116.mbz
moodle2-course-1636-20231118-0140.mbz
moodle2-course-1636-20231120-0155.mbz
moodle2-course-1636-20231122-0013.mbz
moodle2-course-1636-20231125-0018.mbz
moodle2-course-1636-20240130-1631.mbz
moodle2-course-1636-20240130-1735.mbz
moodle2-course-1636-20240130-1828.mbz


As you see, there are 3 forced backups for today and 6 old backups.

Only these files should have been kept:
moodle2-course-1636-20240130-1735.mbz
moodle2-course-1636-20240130-1828.mbz

I tried to find errors in PHP, Apache log files, but nothing useful found.


Any idea why the old automated backup files are not cleaned up?