I had a problem with my pershing when it was new, it could notate the turrent, I found out that the turret ring is getting caught by the fet fins on the DMD only after I glued my rotating gear clutch. Maybe you can do the same, how to check this is remove teh turret ring from teh turret set it on the rotation mechanism and see if its catching on anythingto prevent it from turning. if it turns freely, check the ball bears or what ever mechcanism that aids in turning teh turret to see if they turn freely. if all else fails, make sure your wiring do not get snagged.