[TechniSol]

I'm not one for guessing when it's important, but I suppose if pressed I'd guess that a kepub from Kobo might be more reliable if you're just going to load one book on to test further after a reset/factory reset, etc. than a random epub.

That said, if I still had negative results I'd still reset again and try another, just in case.

I really do think a full factory reset/restore to original firmware might be required if it's a firmware problem. Or maybe you could get away with side loading a firmware? You know checksums are a pretty good way to make sure firmware isn't corrupted, etc., but they are not absolute. You, lucky you, could be the one in a gazillion... (It'd never happen with a lottery ticket, but then I don't buy them!)