Brow deformation shapekeys

I have a “Face avatar result” (one for browDownLeft/Right, browOuterUpLeft/Right ) node which I connect to a “Set” deformation node to drive the models shapekeys.

For some reason both sides seem to get driven together most of the time instead of just the right side if you lift your right brow for example.

I’m wondering if I’m missing something? It works fine if I disconnect the “face avatar result” and feed each shapekey a separate value, so it doesn’t seem to be an issue with the shapekeys.