Hi John
It certainly isn't tight enough to be driven by the RA shaft, sort of flops about when you loosen the lock screw.

I've had a word with Lee Andrews (I think the mount was bought there) and he is going to ask Luke to contact me when he gets back this week and has a look at the parts list. Not into the Goto bit, much rather set things manually. If you don't know how it works, you can't fix it when it doesn't

Thanks for the link, very useful.
Cheers
Bill