The automatic rewind starts as soon as the camera notices a certain resistance. This is a safety mechanism to prevent the film from snapping. Reasons for early rewinding could be contaminations (e.g. little grains of sand from a beach holiday), extremely tightly wound film, dejustification of the auto rewind, and also mechanical or electronic defects. Apart from that you should make sure that a film is not left in the camera for a long period of time, because this can damage the alignment of the auto rewind as well. Film material that is not conform with the ISO norm for film cartridges or does not match the shape of the first cut of the film material, cannot be recognised or transported properly by the camera. Therefore the camera rewinds the film due to safety reasons. Snapped film material is not only infuriating for the photographer, it can even cause severe damage to the mechanics of the camera. In rare cases the material thickness can be responsible for early rewind.
Whatever causes early rewind with your camera cannot be found out by remote diagnoses. We recommend to try out a film of another manufacturer. If the problem is still present, we advise you to send the camera to our repair centre.