I backed my truck over the breakaway actuator on my tandem trailer (please, don't ask!). When I pulled it off I yanked the "handle" forward and seemed to have partially activated the trailer brakes. The trailer brakes are dragging on the disk. The brakes aren't fully engaged though. I tried to drain the brake lines to release the brake but it didn't work. Any advice on how to fix this? I've never messed with a hydraulic actuator before.