It was a fairly recently created project, so it shouldn't have been in yW5 format (I only updated from an older version of 7 very recently, but I've been using 7 for a bit now, so I think the format should be correct?).
(I did figure out how to recover my stuff from autobackups after posting the original message. It was just a pretty concerning issue so I wanted to make sure that specific problem was documented ASAP since I hadn't seen anything like it mentioned in the other posts I'd seen about the scene dragging bug.)