Trying to animate a character but it jumps out of position

I have a rigged character in my scene. I've applied some motion capture animation (idle, talking) to it that works just fine, but I'm trying to add in some facial animation as a new layer in the Animator.

This is how the hierarchy looks:
.

I created a new animation clip and added a keyframe on the facial feature I want to animate (in this case, eyelid_l). Once I created the keyframe, the character immediately jumped out of position on the Y-axis and her pose changed.

Before:

After:


I'm fairly new to animating in Unity, so any help would be appreciated.