My iPhone X battery needs replacing but the Apple Store said one of the screws has been threaded and can't be removed, so they can't take it apart and replace the battery.

The fact that the only place which has performed work on it in the past was that same branch of Apple Store is beside the point here.

Does anyone have experience with this situation of threaded screws in iPhones and how to remove them, so that I might be able to solve this problem for them and get the battery replaced?