Unless your research has turned up evidence to the contrary, I would suggest that that particular issue is likely to be a malfunctioning physical sensor, rather than a firmware bug. Too bad "fixyourownprinter.com" isn't the same thing that it used to be in the old days (detailed teardown instructions and sales of replacement parts), now it just seems to be a forum.

Keep in mind that there's no shame in buying a new printer. I understand that four color double sided isn't pocket change, though. I got one of these, three years ago, after I had resisted replacing its predecessor for far too long. Been happy with it, and having the multi-function scanner/copier features has actually been really useful.