Are your servos connected to comparatively long pieces of metal? If this is the case, the servo just might be moving past the position it is supposed to and overcorrecting due to the inertia of the metal. This problem plagued our FTC robot, and there wasn't really anything we could do to fix it. If this is the case, you might consider having another servo hold this metal stationary when it's not in use. If this is not the case, I have no idea how to help you.
