I think I may have a similar problem with my Nexstar 11 GPS.
My problem now is that something is wrong with my DEC motor. If I press up, then up, up, up... it has no problems. Nice and smooth. If I then press down, the star does a big jump and usually goes off the screen.
If I then press down, down, down...again, no probs. But when I press up, big jump again.
Left and right on the RA drive is no worries at all.
PHD is working brilliantly until it tries to calibrate the DEC motor.
I think my only option is to take the side off the fork mount tomorrow, expose the gear and the worm drive, and have a go at adjusting it until I get rid of this sloppy backlash.
I will let you know how I go.
Baz.
