It's easy to test the motors, just unplug the 6-pin black plug from the DCDS, that isolates the motors. Connect your DC supply to a motor and see if they run freely. If you have a decent meter, measure the current draw of the motors running to see if when freewheeling it stays well below an amp, probably closer to half an amp.
Also, it's important to individually rotate the flywheels by hand through at least one full rev of the drive wheels and check for any binding or change in resistance of rotation. They should rotate freely at all times. If not, you need to address that.
I still think if the DCDS is getting hot that you have a wiring issue.
