Error 001 on display. Contacts between lens are clean!

Contacts have been cleaned, but were not dirty or greasy. Upon closing of the battery door, the red light on the rear of the camera flashes once. Then by switching on the camera “cannot create folder” appears on the display. This disappears after switching OFF and ON again. Pushing the exposure button the ERR 001 appears.

The battery discharged quickly even with the camera OFF. To me it looks like a short circuit somewhere.