That tube is supposed to be a snug fit. If it is so loose it slides in and out then it needs to be re-sized so it has to be pushed in.
Might make sure both the tube and the support are clean, put some locktite on the tube and slide it into place and let the loctite set up.
I don't remember any bolt or other support holding it into place. If it moves inside against the valve cover it will eventually rub a hole in the cover.
