Actually I should clarify a couple of points I made above.
Problem 1.
The Mount. Poorly balanced, overloaded, generally not up to the task (worm gear mesh etc) (ie operator error)
Problem 2.
Communication between the mount and the software. It can be that there is a communication problem between the mount and the software but 9 times out of 10 it's because the operator hasn't selected the right communication parameters in the software.
Problem 3.
The operator. Oh I've already said this.