Trailer brake breakaway failure - possible warranty claim?

Sounds like user error to me too. I don't think that brake is supposed to lock up the brakes, just apply them heavily to stop the trailer. Locked brakes would produce a skidding sled that could go anywhere and won't necessarily stop faster than one with wheels still turning but brakes applied. Simple physics says a skidding tire has LESS grip on the road than one that is rolling.