Thanks to al the reply's !
The problem is not yet solved but you give me some good ideas .
First i had only the A12 back that came with the camera , i schot a few films and it looked good , then i buyed the A16 back but the light trap whas sticky , so i bought two sets (one spare) of light traps by ebay and replaced the one at the A16. after schooting some more film on the A12 back it gave tipical signs of light leaks on the contact print so i replaced that one too , two films later (one at each back) i noticed these signs.
Perhaps i did something wrong by placing the light traps ?
It is not that dificult changing them i noticed...
@Nick Merritt , i bought the light traps by that blackbird711 person
I will tommorow look at it again and try to do some test ,and maybe take ona apart for seein if anything is wrong