Did the change in privacy level happen when a merge was completed? If so, that's working as intended. When two profiles are merged, and they have different privacy levels, the more private setting is kept.
To answer my own question: I just looked at Betts-55 and it hasn't been merged, so I can't see why this would be happening. I suppose it's possible that the Profile Manager changed it, but it seems like quite the coincidence that that would happen right when you were working on it. Hmm...
If you (or anyone else!) see this again, let me know, with as many details as possible re: what you were doing at the time. I'll do some testing of my own, but this one seems like it'd be tough to nail down.