Yeah- as I said the bolt fit would have to be sloppy. The leade reduces the notch depth on the incoming(leade) side and if the milling isn't very good or the top of the bolt is rounded, etc. then maybe the thing can rotate the wrong way.
The other thing is to mark the nipples and do the test to see if it rotates the wrong way every time or on a particular chamber. If it is always the same chamber where the cylinder rotates backwards, then examine the tooth for that chamber- might be a bur, etc. and examine the milling on the leade for that chamber. I had a problem on a modern 1873 Peacemaker. On every chamber full of rounds the thing would jam- I couldn't figure it out. Recoil shield need polishing? Bushing on the cylinder pin too thick, heated metal expanding and jamming? This guy told me to mark each chamber and I realized it was always the same chamber and that tooth was beaten up bad. I touched it up with needle files and that solved the problem.
Any how, before jumping in with irreversible changes- think long and hard about the source of the trouble. I'm just thinking of some possibilities. Wait and see if you get more ideas and suggestions.