Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Welcome to JUST ANSWER small engines, let me try to help you !! I don't know it all, but maybe together we can get you a satisfactory answer!
I doubt it is problem, but go back and check the terminals on the battery, and be sure the battery has not gotten swapped with positive on the opposite end of the battery and now posiitve terminal on battery is in on the black negative cable.
Do you have wiring diagram for the mower? I'm thinking there is a relay used to release the parking brake module. If relay is stuck, it would power the brake as soon as the negative cable is attached.