Hmm. Strange, that. Even stranger that of the two ao3 fics I provided, one posed no problem, whereas the other did.
But, since you mentioned calibre's
modified date throwing things off: would moving the file from one calibre library to another count then? Because that I did. (Also true that timezones differ, I think. Mine is gmt+1, not sure what the timezones of ao3 and ffnet are, probably some American timezone.)
In fact, because you mentioned it, I've tested it out: I moved a few files that have new chapters that I didn't download yet into a new library, and when I tried to update, even the epub file would not allow it unless I overwrote. So yeah, that might just be it as far as problem source goes. But, I'll install and use the test version anyway, and get back to you with its debug file.
But you're right, I do get email update notices, so might as well use overwrite always, no reason not to. As long as I can update and download at all, I'm happy.
