My error it is the other way around, too late to change my post above.
Originally Posted by hmzimelka
In terms of film bulge, on 120 SLRs you can check this with "B" and press the tip of a pencil on the film to see if it indents. You know the film can never bulge backwards behind the pressure plate unless your pressure plate is bent. So even if the film has a curve to it, when it gets squeezed between the film gate and the pressure plate it can only bulge in one direction...toward the lens. I will say that I have not had a camera that did it consistently with all films, so you may have a lens issue as others have pointed out.