The cylinder on my SP101 (9mm) locks up when I try to thumb cock it for SA fire. It only does this on one cylinder stop, but does it consistently. The cylinder locks up completely when I try to thumb cock it, but will cycle when I pull the trigger for DA fire. I have examined the stop on the cylinder and the ratchet and cannot find any burrs or other problems. This just started after my last range session. I have disassembled it a few times to see if something was out of place and have not found anything. Does anyone have nay ideas before I make a trip to the local gunsmith or send it off to the factory? Thanks.