I was given a Pentacon Six new from the factory on a visit to Dresden in early 1970s. Right from beginning there were overlapping frames. Shortly thereafter when back in US traded it in for a 400mm Telyt for Leica. Only afterwards did a very good camera mechanical tell me he could fix it. Since mine was brand new, I don’t think cleaning is the answer, but possibly it can be fixed, but I have no idea how to do it.
Too bad, because handles well for a big camera and feels better in hand than Pentax 67. Was able to get a pic of author used on dust cover for his book. Everything worked but frame spacing.