Is there another brute or prairie he can swap parts with to chase down the problem. I figured mine out by swapping the actuators between axle and brake one. When switched them out it stopped acting up. Replaced 4x4 one, works fine now.
There is also two relays underneath the seat that also can go bad. There was a good thread about a year ago that really got into solving the problem. I believe it was started by JMclure.