My SP101 does the same thing. If I pull the trigger starting with the cylinder latched on the bolt from the last shot, it's no problem. If I half cock and then lower the hammer, stopping the cylinder half way through its rotation, pulling the trigger will not complete the rotation - it just binds up hard. Upon thinking about it, I realized that the pawl/hand is out of alignment with the cylinder ratchet if I start with the cylinder half way advanced. So the pawl hits the high part of the ratchet and just binds up. I believe it has to do with the longer 72 degree arc that the five shot ratchet/cylinder has to travel through.
My solution: don't do dumb things like advancing the cylinder a half stroke before pulling the trigger.
