Sorry if this is the wrong board.  I figured carpentry was the closest.

Most of the doors in our house have still got the original rimlocks on them.  I've slowly been going round cleaning them up and repainting them as the look awful covered in gloss white.

This one has got an odd fault though.  When you open the door, the latchbolt pulls in too far and lifts slightly which stops it coming back out



I've opened up the lock, and everything inside looks as per the others I have dismantled



Anyone got any suggestions how to fix it? I'd rather not replace it as it is original from when the house was built

An option might be to make a U shaped packer, basically a rectangle with a square cut out. The square hole would be the same size as the bolt. If you then glued this to the inside face of the lock the bolt would not be able to slide inside the lock and jam as the shim would keep it square. If that makes sense.