I tried to post on here yesterday, but apparently something was wrong with disboards.
New info: I called member services Saturday and couldn't even get through to a live person. It just said all representatives were busy, call back and later, and hung up on me.
Yesterday (Easter Sunday--apparently most people assumed they were closed, because I was told that the call volume had been quite light all day), I called and got right through. I was told that even though the VGC online booking tool was down for members, that member services could cancel, modify and make VGC reservations. I got a bunch of info on my points from her, hung up to make some decisions, and called back. The 2nd rep I talked to checked with a supervisor and said, no, VGC was down for even them. I called back a 3rd time, rep said no. I waited a while and called back right before they closed . . . #4 rep said YES they could cancel/modify/book. He cancelled 2 reservations for me, modified another one and booked a new reservation (all VGC).
This explains why the availability has changed despite the "system being down." I had seen 3 consecutive days in August that I wanted to book, then it changed to 5, then to just 1 available in that week.
So, it is possible, if you get the right representative, to cancel/modify/make reservations. And there had not been any changes to my previously existing reservations during this April glitch.
Hope that helps someone!