Bronica ETRS 135N not winding when attached to the camera

I have a strange issue. I have a 135N film back to shoot 35mm film. When loaded with film and attached to the camera, it does not wind. The frame counter would move off "S" does not reach "1". Winding the film only cocks the shutter but the film does not move. Have anyone experienced this? The film back appears to work as it should. I am out of ideas. If anyone has any ideas, I would like to hear it.

For information:
1. It is not in double exposure mode.
2. My 120 film back works fine.

Thanks

I do not have direct experience with it, but I suggest:
- with the film back off the camera, try turning the main wind gear with your finger (as the camera would) to see that the back really is winding.
- check the pins that communicate between back and camera; if these get sticky it is often a cause of trouble as the back and camera don't communicate the wound/cocked state.

However, I think the camera must sense that the back is attached, or it wouldn't cock the shutter. I tend to suspect the back - when you say it seems to work, what did you test?

It is the back. When the door is open, I can see the film transport working and winding as it should. It winds to the end the film. But when the door is closed, I can never get to the end of the film and the frame counter does not advance. I then removed the back and marked the test film with the dark slide removed. Inserted the back and shot a few frames. I then removed the back and dark slide. The marking I made to the film did not advance. I have returned the film back to the seller for refund. It is a shame. I was planning to convert it to a 135W film back.

For information, this issue was resolved. I ended up making a deal with the seller and kept the film back.

I opened the film back and found the pin that gets pushed by the camera was not going far enough. I worked and oiled the pivot with a small of oil. That was all that was needed to resolve the problem.

Good to hear and thanks for the update.

I don't have a vast experience to draw on, but think when the Bronica interchangeable back cameras have wind issues, it is often traceable to similar pin / communication problems (dirtiness, possible weakness of spring, etc).