Did you rule out all problems? Like saddle, teeth, back, etc.? If so, how do you ride? I mean are you balanced? Are you clear in your cues? Some horses buck when they are confused and/or uncomfortable (if you bounce all over). I think disengaging is great when horse does it to test you, or being fresh, or just being moody. But if the reason is pain or inability to ride disengaging won't fix it, and turning tight every 2 mins won't teach your horse not to buck.