FYI - I had this same problem. I disconnected the linkage to the breaks so I could move the machine. I then stopped at a dealership and picked up a new BCM. Only took 10 minutes to install. I thought I was home free. Not so much. With the new BCM installed and connected, I still had problems. The brake actuator would partially move. The mower would start and charge, but engaging the blade killed it after 10 seconds.
I thought I had installed a faulty module but when I went back to the dealership, the tech asked me if it was possible there was corrosion on the pins of the connector. I went home and spent 10 minutes disconnecting the harness to the module, inspected it and found corrosion on 2 of the pins. After a thorough cleaning, I reconnected the module and bang, everything now works fine. In my view, the problem is not a faulty module, but the connection between the harness and the module.
Dirt and moisture can get in even though there is a cover over the assembly. I removed the new assembly and put in the old assembly and it worked fine. Perhaps there are cases where the poor connection can cause the module to fail? I don't think there is a problem with the assembly, there is a problem with the connector and corrosion. I have now completely wrapped the harness and connector to the new assembly with electrical tape to keep it weather and dust proof. Try this before replacing your BCM. It only takes 10 minutes.