I have the opposite problem with my Koni - occasional overlapping frames. If you can, get it get repaired, if not you just have to get to know it. I pay close attention to the way I advance the film (or slam the hammer, as I sometimes think of it), and I've figured out that a firm but slow pull works for me. For non-DIY repairs, Greg Weber <firstname.lastname@example.org>, is the man for Koni-Omega. He's also very reasonably priced. Good luck - these beasts make incredible images!