This problem may be caused by a small amount of misalignment in the camera. It concerns a part called “pick” which ist visibly when peering into an empty camera before inserting film. It is in the extreme left corner, a small silvery hook normally feeding the cover sheet or the next picture to be processed just far enough towards the camera´s rollers tofacilitate transport by them. If slightly bent it slips over the cover sheet or the picture frame without facilitating froward motion.
It my be gently bent slightly downwards with a dental pick or likewise to ensure reliable function.