It could be a mulitude of things. Mine was cause by the training gear but they too use to vibrate. I cut them down and problem went away. It could also be main blades out of balance or track, the gyro gain not set up correctly or something slightly bent. If there are any other flyers aroung get them to fly it without the training gear on and this will tell you immediatly if this the problem. Has it alawys done this or has the problem just started?