They are. The only thing that could possibly cause an issue like this is if the game crashed while it was writing to the save file, or if there was corruption on disk i.e. bad sectors etc.
Online, there are other possibilities. But offline, that’s about the whole of it.
A sensible assumption, but the recent status update would seem to suggest that isn’t the case here.
Nonetheless it sounds like a fix is coming. For the time being they advise people not to use the same name for online and offline characters. Though that doesn’t seem the only issue at play here.