Are you loading the camera correctly? When the film is loaded correctly the film runs under a felt bar on the left side, over the film guides and then under the guide roller next to the sprocket, then onto the take up spool. Is the film tight when you load it (push the rewind button in once the camera is loaded and tighten the film up-then wind the film on again)
Also is the rewind spool free moving? If it is tight it can put too much tension onto the film and cause overlaps in some cameras?
I've used and repaired maybe 8 or 10 widelux's over the years, and I've never seen one overlap films? Does it happen on all films - 24 and 36 exposure, and at the start of the film, the end of the film, of through the entire film?
Let me know and I'll give you some ideas - these cameras are pretty easy to pull apart and do basic repairs to...