Mine is bought brand new and have ocassional film spacing problem - 2-3 rolls had 2 frames overlapped for about 1/4". I suspect that my hand might be touching the rewind structure during winding, not sure. The winding, seems to me, is not as solid as a Leica or a Nikon FM/FE series body. (Some say the ZI is based on a Nikon FE body)
Also, once light leak on 1 frame that I keep scratching my head why it occurred. Very weird.