That was my first thought... but the behavior is uniform regardless of the source of command input. And I did investigate the worm mesh. It is very binary in that on command it either moves or it doesnt. And when it doesnt there is no indication that the motors are straining against something. In fact, there is no indication that the motor is being powered at all. So I have turned to looking at it as a software/electronics issue rather than mechanical or traditional 'user error on device'. The RA axis exhibits none of this.