So I stopped by my local shop yesterday on the way home and I was asked to look at a model 60 in for a cleaning and repair.

The claim was that the cylinder was 'skipping' - upon examination of the pistol it appears that the cylinder stop, every once in a while in double action, will not fully extend up out of the frame and engage the cylinder notch itself. Thus the cylinder can still be rotated.

Having not had the time to take the side plate off an look at the internals. What would be your initial thought, if you saw this on a visual inspection, without having had the chance to look at the internals?

Stop spring broken?