Why is my lightsaber glitching every time it moves?

I have a Luke green lightsaber from Disneyland. As soon as I turn it on, it's fine but as soon as I start to move it, it begins to glitch. The lights and sound flicker. It sounds as if the motion sensor is stuck in one place, and it keeps going back and forth. I've already tried taking it apart the hilt to see the problem but have had no luck so far.