Cool, I didn't know that. Thanks for the info! Unfortunately, I've already repaired it with the plaster. If it comes off again, I'll repair it with that. Thx
Köpfchen gave the right advice: put the spacer rings on the empty box. Of course, screw the spacer rings onto the empty box. If you want to do something good, putty the gap between the plaster and the spacer ring. Then screw the socket to the spacer rings with suitable screws. And if you then tighten the claws a bit, it should hold until the next Stone Age.