@Calleja: Calibre should be able to tweak the cover without stripping DRMs (IIRC).
That's interesting, though. Would you be willing to PM me the file (DRM'ed, don't care about the content) so that I can look at it?
I was gonna ask what you see when you 'Go To > Cover', but you answered that, so, yeah, I'd really like to take a look at the file

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