Photoshop Elements 18 Backup Error

Hello. When starting a new backup procedure in PE 18, I get, after initial file preparation, following error - and all stops.

In english: error while writing file   <<path\catalog.pse16db>>

As message is definitely vague, I really have no clue. No issues of disk space, of which I indeed have plenty

Anybody could  kindly help me please?!

Thanks in advance