Animator layers with higher priority preventing others layers from working?

Hello guys, I'm quite new to Unity and I have a problem with Mecanim. Basically, I have few layers - Base, Both Hands, Left Hand, Right Hand. All have appropriate Avatar Masks. The problem is, that I have a fast attack (shoots a fire bolt) that switches hands after shooting, so it's first right and then left hand. Right hand anim overwrites the left hand anim just fine if I shoot fast enough, but when it comes to left hand, it doesn't want to overwrite the right hand transition and I need to wait for it to end or the left hand anim won't play. In practice it looks like I'm shooting with right hand only if I'm clicking fast enough. Is there a way to force that Left Hand Layer to overwrite Right Hand Layer?