Electric trailer brakes are a very well-engineered products. With few moving parts and no fluid to leak, they are as close to trouble free as any brake could be expected to be. For this reason, when there is an issue with electric brakes it is usually quite quick to diagnose. However most problems with these brakes are in the wiring and are not mechanical problems.
Start with the Tow Vehicle
Many times when electric brakes fail or work too abruptly, locking up the wheels with even light brake pedal pressure, the problem is in the brake controller settings. Therefore, with any electric brake problem except a noise in the brakes start by checking the controller. Watch for the controller to light up to verify that the controller has power and turns on when the brake pedal is pressed. Next, check the adjustment knobs or sliders on the controller; sometimes these are hit accidentally and become essentially turned off.