Jake brake won’t shut off with throttle pedal???

Hey guys, I’ve got a big cam 350 Cummins in a T-600 dump truck. This morning on the way home I was using the jake just like all night and when I got back on the throttle the jake didn’t shut off and it seemed to back fire when I was back on the throttle. I have two individual switches, one must control two heads and the other just one head. I was using both when this happened, it happened a few more times. Then I figured out it I shut off the switch that controls just one head it shuts off with the throttle and functions normally. If I switch the second switch back on it messes up again. Do I have a bad solenoid, switch, or what? Thanks in advance for the help...