Hi Adrian, I was just re reading your issue with the binding rachet and have had a similiar event. I dismantled the gearbox, groan, and percieved that the bronze bush on the inner end of the shaft was worn and allowing the shaft to float inwards. There should perhaps be a thrust washer in there to prevent this wear. Anyway, i measured the endfloat, found the appropriate thichness and ID washer and have put that in. It has fixed the problem. However i should add that it would be much easier to just replace the bronze bush as it is very difficult to reinsert the shaft with the washer on it.
Hope that helps
Ben