MorphTargetInfluences Revert back to 0 after being set

I have a tongue that I am moving through blendshapes it works, however as soon as I let go it snaps back to it’s original position…

 const tongueBind = useDrag(({ delta: [deltaX, deltaY], down }) => {
  if (down) {
  tongue.current.morphTargetInfluences[0] = tongue.current.morphTargetInfluences[0] + deltaY * 0.1;

How can I cause it to stay in place?