I would take it apart and give it good cleaning, including the trigger assembly and the inside of the receiver. Could just be some crud build-up in the receiver channels and shell stop recesses. Test the trigger for smooth operation after a thorough cleaning.
Take it apart and clean look for broken, bent or binding parts. Reassemble and check operation as you put the parts back in one at a time. You should be able to find the one that is binding as it goes back together. It is possible that someone put the wrong part in the gun as there were three different series '31, '34 and '41 as I recall. Some parts were different in each of the series and those inside might not fit properly if not matched to the series. I think that one shell stop was different and possibly would bind if not the correct one.