I started this as a new thread to get Johns attention. What I want John to look at is the small screw to the left of the winding/crown wheel. I'm thinking that this is for the watchmaker to lock the clutch in the winding position. It might not be released all the way. Let me know what you find out.

Thanks for the link to the manual Lawrence, appreciated.
I checked the screw you mentioned, but it was clear.
Wierd one this though, I checked the operation of the setting wheels and mechanism in the donor, and it all appeared to operate ok, swapped the whole shebang over, and the same problem's still there!

I can only put it down to excess wear in the bore the stem end rotates in, plus the end float on the gear up and down the stem that I can't get rid of.
If the crown is moved in short arcs all's ok, but move it in a continuous run and the gear teeth climb over each other as if the tooth ratio is slightly mis-matched - same happens with both sets but only in this watch, not the donor!

Back to the drawing board!

Thanks again,
John

Maybe you'll have to set this one aside and think about it for a few days. This usually works for me when I have a trouble watch on the bench.