If it twists so much it tries to shed the string, it' s probably a wallhanger. If it just twists a little, then you could heat the limb and twist it the opposite direction it wants to go until the limb cools. I' ve corrected a lot of twisted limbs that way.

I' ve come to like heating limbs under hot tap water in the bathtub, but you can do it with a heatgun or over a hotplate too. Heat guns and hotplates especially if the finish doesn' t seal the wood well, but if the finish is in good shape, the bathtub treatment is best, in my opinion. Just be darn sure you don' t get the limb too hot to handle comfortably or it will delaminate.