Tom57, Surely you understand the faster things spin the more centrifugal/centripetal forces they suffer. If something is seriously unbalanced by a failure of a support strut then this could happen. All you have to do is look at what ground resonance can do. A helicopter is naturally unstable and a slight variation can change a lot of things.
https://www.youtube.com/watch?v=0FeXjhUEXlc