W124C Folding seats not working

[Boinkers]

Hi all.

I just managed to get my old Brabus 3.6 CE through Swedish immigration from its native Germany. Yay! But, it has been sitting still for 6 or more years so it is in need of some love to get it up to par. One thing I have not been able to figure out ; both front seats have folding backrests, which I suppose should be in a fixed position when upright. There's a button on the side of the backrest which looks electrical in nature to release the backrest...but. Both backrests are moving freely back and forth, something the authorities here doesn't approve of very much.

My question: should I look for a mechanical or electrical solution to this problem? Anyone know how these seats are supposed to work? The car is from 1988.

Any and all suggestions will be most appreciated

/Pontus