The rest of it I guess. Part way through a roll, the camera jams and I can't advance the film. The problem is that the spool in the Holga doesn't exert enough tension on the take-up reel. The film then winds on to the take up reel to loosely, taking up more room than it should and jamming the camera. Tape the sucker up or buy a Rollei.
Light also leaks seem to change from camera to camera.
See Taping the Holga for details. If you don't have the facilities or aren't interested in doing that yourself, find a good professional photo lab in your area.