Reset shape key for mouth without wrecking my lipsyncing process

I made shapekeys for the mouth, spent a while lipsyncing, then noticed one shape key also moved the arm somehow. How would I repair this without losing my progress?

Hi there!

You can create a Vertex Group of only mouth vertices assigned.
Then use that group to restrict the shapekey influence just to that area.
Then add “New Shape from mix” to create “clean” shapekey:



Thank you so much! You saved me a lot of pain!