premium display?
that probably means it has a motor controller for hydraulics correct?

if you have all the switches disconnected and the motor still runs wide open? that sounds like the power transistor in the controller is shorted.

i would check the motor and cables but i think you'll find the problem in the controller.

when you have all the hydraulic control switches connected while it is doing this are there any codes on the display?
if you go into the fault history are there any hydraulic codes stored in there? That will probably tell you what was going wrong before this happened.
In case your not familiar on how to do this, go to the display and press the * key or #5 key and hold it with the keyswitch turned off. It should display all the traction codes first, then go into the 3 digit hydraulic codes.