My Stereo Kodak did the same thing. I found the pressure plate didin't have the spring it used to have, and was allowing the film to slip over the sprockets when the film was wound.

I re-tensioned the pressure plate (pulled it forwards a bit - this bent the springs back and made the the pressure plate push against the film better) - this seemed to fix 98% of the problem.

Now I also wind on fairly slowly..This seems to have fixed the problem. I get the occasional very slight (less then 0.2mm) overlap on the odd fame - but this is covered by the slide mount anyway..

I suspect a prat of the problem is the fact that modern film has a thinner base than classic films such as Kodachrome, and this causes the slipping...

Also if you do a search on the new you can download a copy of the instruction book

Have fun