Hmm.. maybe try clear_bones and https://docs.godotengine.org/en/stable/classes/class_polygon2d.html#class-polygon2d-method-add-bone? (I can’t add another link for some reason…)
That would be strange if that fixed it though, as I suspect it just sets the bone weight under the hood. The only thing I can think of that might fix it in this case would be setting the node again via the node path might bind it to the TwistedIK2 bone rather than the Bone2D node.