If you have a shake in your heli and you have had a blade hit the boom or tip over. Check the long balls on the swash. I had a a bad auto that caused my heli to have a small boom strike and after looking over the heli i started to fly again and the heli had a shake in lower RPMs. Checked the heli over when i got home and found one of my long balls on the inner swash was a little bent. You could see it while unscrewing itout of the swash.