Sounds like the hand is worn and finding another hand could be a real adventure. It also appears that your cracker jack smith put it back together incorrectly. Does the side plate match up flush with the frame? As I remember the bolt is cammed by the hammer and I suppose something could have gone south there. If it turns out your hand is worn there are things you can do to 'fix' that I would try, but only because I don't know any better.
I tried to find a web picture of an OP or a python with the side plate removed but woas not successful.