knob for the switching between modes moves fine, it just never goes into direct drive.
I just had a thought. If you don't have another Rotex for comparison, it may be that yours is working fine, but you don't know what to expect.
In Ex mode, you can turn the pad around by hand, just like an ordinary random orbit sander.
In Rot mode, you can still turn the pad, but there is a great deal more resistance. The motion isn't nearly as free as in Ex, and it isn't simply rotating. A Rotex pad never
It definitely sounds different in Rot mode. I think of it as growling.
And last, it feels different in Rot mode. Better keep two hands on it. Ex mode's like any other ROS.
Try to compare it with another Rotex before you ship it off for service. Even a new model Rotex should give you a clear idea of how the two modes differ.