Avatar mask not working

I’m making a humanoid animation, where the player can run and aim at the same time, but when I use the avatar mask for it, the player’s animator get weird, and some animations don’t play when they are supposed to. The only override of the aim avatar mask is the two upper arms and the head.
What is going on? Is something wrong with unity??

This is what my aim layer override is (I only want it to control the arms)

I got the aim mask to work by putting the aim layer under the default layer, and setting it’s weight to 1. Before, it was above the default layer.