Hi. I've recently bought one of these for my SQ-Am. It came with full instructions. There is a sheet that tells you that you may need to fine-tune the fit if you experience difficulty firing the camera, or removing the back. The exact wording is;
"
If you are experiencing difficulty in firing the camera, adjust the slotted set screw in the film chamber counterclockwise.
If you experience difficulty in removing the NPC Polaroid back from your camera body, adjust the slotted set screw clockwise.
Make the adjustments 1/4 of a turn at a time to insure that both the firing and the removing of the Polaroid back can be achieved. Be sure to select a screwdriver which fits the slot in the screw snugly.
Remember: before using the NPC Polaroid back on your Bronica camera, first set the switch on the camera body to multiple exposure mode. "
I have not had to do this as mine worked ok. It will come off with the darkslide in or out, so remember to replace it before removal to avoid wasting a frame. There is no picture to show where the set screw is, and mine is loaded at the moment so I can't check it. I hope you get it fixed. So far, I am very pleased with mine.
Alex