Hi Jared,
I suppose there is some current surge issue causing the disconnect. Do you have the axes disabled when you plug in the supply? That might be the difference. After a KMotion re-boot everything will be disabled. I doubt if using a switch vs plugging in the AC plug will make much difference.
Use the Step Reponse Screen to diagnose issues with the higher speed motions. Setup a similar distance and speed move and plot Command, Position, Output vs Time to see exactly what is going on. Post screens shots (I use alt-Print Screen, then paste into Paint, then save as a .png file) of your Step Response, Config, and Filter Screens and we can probably help determine what is happening.
Regards
TK