Hmmmm, last night I set Backlash to Zero on both Axis. No change. It is exactly the same as when set in the thousands!
Fortunately I remembered to re-balance the mount first.
I don't know what I did, but my GoTo's are out again
I must have slightly moved the mount when I shifted the counterweight.
Anyhow, the slew drifting problem is still there.
When I grab the end of the counterweight bar, I can move the mount in RA a few millimetres back and forth!!! That can't be good.
Also the Dec moves about 1mm when moved by hand.