Hi, I could know what is making this annoying problem. I got same with my Bronica and I just opened that filmback. There's lots of screws but not so much other stuff. Anyways I find out that when you wind film from starting position to 1st frame, when you got to the first frame filmback locks. Its because then camera part starts to load itself. And when you fire your shot then -- there comes hammer from camera and it picks to the knob in the filmback and releases the film for going one frame towards and then it locks again.The winding mechanism doesn't seem to want to wind the film on past 1st marker.
When I first got the Camera the chap I bought it from popped a test roll in and showed me that it was winding on and I noticed the counter progressing.
So I just put little bit bike oil to that knob and everything works fine finally. If you look your filmback from camera side you can see on the left side wheel, below that is circle shaped hole and below that is vertical shaped hole and that is where camera picks. Put oil there and it could work. If you want to be sure that you don't mess up thinks with that oil, then you maybe should open that metal plate which is locked with screws. And then you have chance to oil whole mechanism. Just put all the part back with care.