I wanted to share my experience with
MDE staying at SOG the 3rd week NOV 2018, as a guest of a service member. When we first linked our SOG reservations, both ours and the other family's reservations linked with no problem, although after a few weeks ours disappeared completely and Disney doesn't have any record of it, though SOG still did. This worried me at first because of making FP+ selections at 60 day but I was told by Disney that as long as the other reservation still showed up, I can make FP+ selections through the service member's res because it was still showing up and we are all linked.
Fast forward to 4 days before my 60 day FP window and neither reservation is showing up, so I am on full panic mode. I call and log a ticket that day, and then the day before my window begins I call again, but still nothing linked. Im on hold for about an hour, but THANKFULLY the Disney rep in the MDE website dept tells me that they will make all the FP+ selections for me (a day early) and attach them to our MDE account. So she stayed on the phone with me and I was able to get all the FPs I needed at basically whatever time I needed them. They really went above and beyond to fix their mistake the best they could, and really save our trip. I would suggest being very patient and nice with them and tell them exactly what you need and I know that they will do their best to help.