Take a look underneath and see if a wire has chafed. This is especially problematic with series wired brake systems where the brake wires are led through an axle or not secured correctly. If you really want to get the power to each brake, rewire the brakes in a Star configuration, two wires from each wheel led to a junction terminal on the tongue and your primary brake wire from the umbilical connected to those individual supply wires. This will get more juice to each brake assembly and is easier to diagnose a brake problem if you have one.
Good luck with the brakes.