I recently cleaned and greased my old Slavia 631 and after i reassambled it it would sometimes fire when i took it of the safety
Without pulling the trigger
Without pulling the trigger
Did that 6 times all I could see was the spring a little bentSorry I don't know anything about Slavia 631. If I was you I would disassemble it and look around to see what went "wrong". I've disassembled and reassembled and had to disassemble again and have a "there it is" moment I've had safety tiny spring/ball issues before mess up my trigger I don't know if the 631 had the same tiny spring/ball in detents or not?? Good luck..
Glad you figured it out, but if it acts up again try replacing the spring.It kind of fixed itself after shooting it a couple dozen times while holding my finger behind the trigger while pushing the safety