Electric Brake Randomly Locks Up

[Sherwolfe]

Having an issue with my left front trailer brake. It will intermittently lock up but only when the speed is under or around 20mph. So I have pulled the wheel down, looked at the brake and all appears normal. No grease, contact magnet looks good and clean. I also checked the ground wire at the frame as well as a good look at them around the axle, including the inside of the brake drum.

I've traced the wires as much as I can and can not seem to find any loose or broken or worn wires. This lock up only occurs on the left front wheel, and is very intermittent which makes this even more frustrating. My gain for my Ford controller is set at 6 and none of the other tires are locking up. At higher speeds all seems to work just fine.

For those with Ford trucks, I did just recently have my trailer brake controller updated with the new software, well actually when Ford checked it they told me mine already had the updated software. So now i'm out of ideas on what might be causing this issue. Any troubleshooting ideas would be appreciated.