So, finally my retailer answered....

To make it short: They are perfectly sure having used the SFS file system.

This raises two questions for me:

1.) What kind of (bad) error I have which obviously changes the file system from SFS to FFS (at least it is now recognised as it) but on the other hand is not that heavy so that I can access files and drawers...

2.) Should I give SFSDoctor a try after all?

Thanks!