It's only gone and done it again. At least it's now been pinned down to me most likely doing something horrendously wrong with making the door seams, as that is what seems to trigger this in both yesterday's and today's model. And to add salt to the wound, I had overwritten the copies that were made in between last night and now. I only have one other backup from a week and a half ago. I'll see what I can salvage from them.