Cross pin is a very good place to start. Slipping can sometimes be caused by a bent axle shaft or tube. Take a look when you have some time. You can send me pics of the teeth and I will let you know what I think. If you are still having issues, I have a C8.25 scratch and dent she can have. Some of our older 8.25 Australian units had a bad couple batches that were replaced under a warranty recall. Do you know if her locker says 'made in USA?'