OP - It's probably just the ground. I had this issue as well, sent my box back to JDP and they fixed something inside of it. Recently I had the same issue again so I took the wheel well screws out and played with the ground on the horn - seemed to have fixed the issue temporarily. Going to get a new ground location and one of the washers that bite into the metal for a better ground.
See if this fixes your issue too. If not call JDP for sure! They're very helpful.
Edit: Just to be clear, you're holding the brightness up & down + power for 30 seconds, unplugging the fuse for battery power, and still holding the buttons for another 30 seconds? Then the remote should be reset.