try just snugging up the blades in the grips.

i went through the same thing with my 3dpro...round and round balancing, rebalancing, checking, double checking everything in the head. ended up just torquing the blades down and its smooth as silk---not so tight that they cant straighten themselves when the get spooled up....but, tighter than normally recommended.

there are a multitude of things that can cause the shakes. this may not fix it...but, its a simple enough procedure to warrant a try.

good luck.