That's what I have too but maybe I just got lucky. I was seeing it a month or so ago. I'm also working in a different project now so that's probably where my "luck" came in. I was going to contact Support about it, so that's what I'd suggest for you.
I deleted the file whose file extension indicated it was the supposed saved NameMapping data. Maybe works. I am awaiting a repeat of the symptom (or lack thereof) before determining if that is the "solution".