<p>It sounds like a problem with the film/shutter interlock inside the camera. The C33 had a lot of variations, though the only externally visible one was the option to use a 220 back. The 220-capable models have a small cut-out in the chrome at the top right of the back, and a second film counter reset located there. It does not sound like this body has the 22 option.</p>
<p>The only other thing to check is that the toothed wheel inside the film take-up chamber is evenly sprung. This is what measures the actual film advanced. If that is misbehaving, the counter will be off. I usually use a sacrificial film or just a roll of backing paper if I want to exercise the transport.<br>
<br />The C33 back is thicker metal than the later models, but it is also worth making sure that the back is fully latched in both corners. I suspect a problem with the internal mechanism.</p>
<p>I have not updated my web pages recently because the Mamiya stuff has not changed. It has been around twenty years since the last of the Mamiya TLRs were made, after all. And I certainly don't consider myself a 'world authority'. I just collate information!</p>
<p>Graham</p>
