The Simulink Rover Control models works fine up until the servo section. I switch from OFF to ON, and the servo gauge is between -1 and 1. It moves down to its lowest position, then I get this error.
Another note, In the setup video the 3 pin servo connector slides on the way on, but mine is tough and there is about 2mm of space. I pressed fairly hard and it would not go in all the way.
I also tested it with the script from 4.1 and the servos worked.
You say your problem stems from the servo. That you "pressed fairly hard" will need you to verify the nano and servo works "offline" (just Nano, Servo, Power Supply, no other boards, communications or apps). If your Motor Carrier is not the problem, then I would look at the power supply... you describe the beginning of the error message as when you moved the servo, then the error XCP occurred (that is the communication link). My guess is the power dropped low enough for a brown-out condition and the first thing to stop working was XCP.