Agree with Raytech, Check the wiring circuit associated with your brake. I have had a couple new trucks where the brake was engaging and disengaging during a work shift (with deadman depressed) and went on like this for about a week till the wire finally broke completely and entire brake system, pad, rotor, electric magnet got toasted after the operator drove it acrost the entire warehouse. When this first occured I couldn't figure out why it was doing what it was doing but after it finally failed completely we figured it out and know what the signs are.

Since the raymond motors move and all the wiring connected to them moves, the wires break. Especially where the wiring is firmly tied down with zipties and one side is moving back and forth all day long.