Observation/question about my paterson

[namdoc69]

While I had the cylinder off the pistol frame last evening, I discovered something interesting, if I cocked the hammer and released it by pulling the trigger, after about the third time I did this, the hammer locks up, can't cock it again. I was watching that rotating collar on the arbor that turns the
cylinder, when the hammer locked up, I moved that index pin on the collar
just a bit and the hammer would cock again.
For anyone that owns a Paterson, is this normal? Does a cylinder have to be on the frame for that collar to function correctly. Just wondering.