Multiple Layers Animation [Mecanim]

Hello
I have a strange problem with mecanim. There are 3 layers of animation in my project(basic, pointLeft, pointRight). The second and third layer have animation for left hand and right hand only.

I am using body masks to apply animation only on left hand and right hand respectively and works fine when i am animating only 1 hand at a time… but when i try animate both hands one of them doesnt work properly and just starts flaping …

Are there any issues with using multiple layers with body masks in mecanim or anybody knows a solution to my problem?

Thanks!!!

Do you blend the layers like: 2nd layer = left Hand, 3rd layer = Right Hand?
Are you using òverride`or additive?

Cheers.
werner