First things first. When you say you are moved all around, do you mean within F or are you being moved to seats in Y? If you are being moved to seats in Y, your itinerary may not have been reticketed after SWU application and you should call pronto to have them do so, and don't take no for an answer, so that you are sure you are actually going to fly F.

Assuming that you have been reticketed and are actually in G, are you sure there have not been equipment changes? An equipment change is always "possible." Leaving aside valid explanations, DL's seat reservation system is screwy and this seems to happen frequently. The only thing you can do is continue to check and switch back when you see a change. OR, there is an app for smartphones, the name escapes me right now since I don't use it, that will alert you supposedly immediately when there has been even the slightest change, so you can attend to it right away.