Cleaned and tested continuity for ground to motor and for brake switch. All tested good. Re-tested starting the motor. Same issue. But...I thought 4 post solenoids didn't matter if they were grounded. Wouldn't work if not grounded. When I grounded it and starter kept running even with key off, I lifted solenoid off mower frame and starter shut down. I reversed the battery and starter wires on the solenoid to see if that mattered, and same issue. Solenoid did not work if not grounded, but when grounded starter keeps running until ground is interrupted. Beginning to wonder if possibly the new brake controller is defective? I watched when key in run position, the brakes disengage when steering levers are moved. So it appears to work that way...