Looks like not many ideas here, so I'll try one....
Looks like not many ideas here, so I'll try one....
I do know that if the film is not winding tightly on the takeup spool, it may jam sometime during advancing, OR it may jam as it is coming back off the takeup, ie. rewinding.
This is very common on horizontal transport medium format cameras. It can also happen on 35mm like your ZI.
I experienced this a couple of times on my Kiev FSU, when the screw on the takeup spool loosened. I always take care to close the film door on a new load with tension on the winder. I always check during advancing 35mm or otherwise to make sure the film is tight in the camera by checking tension backward on the rewind control without releasing the film.... JUST VERY SLIGHT tension to snug up the film.
Film will tend to pile up with any looseness in loading. The 35mm cassettes minimize the process, but it's a big item on 120/220 rolls. You may be experiencing this on your 35mm.
If you still have a jammed rolling your camera, you may need to just dig it out after opening the camera. If you do open the door, take a look at the takeup roll and see if the film is loosely wound.