NetQvist
All guessing on the serial number part and EVGA is refusing to let any official info out.
One thing you wanna be careful about is that if you RMA from EVGA you might be stuck in their circle after that and then you'll not be able to exchange the RMAed card with your seller after that. Myself I'm taking the seller route because due to the little info EVGA is giving out, going to try to exchange it for a MSI or ASUS to begin with so I never have this issue in the first place.
I really do wish that EVGA would issue an official statement on this issue so that people aren't left wondering if they are going to get another defective card.
At the moment, I'm a bit unclear if they are just sending out replacements in the hope that newer built ones are more reliable or if they really have fixed the issue and we are guaranteed working cards (seems not if ElBarToME's post is anything to go by). From this thread, it seems like a lottery as to whether you will get a card that is free of the issue and, in my case, this issue did not manifest itself until almost two months after I'd bought it so while it might appear you have a working card now, whose to say it won't develop the same issue in a month or two...?
I would have much preferred to have returned my card to Amazon as, IMO, they have by far the best support of any retailer I've dealt with and do not ask for insultingly large collateral payments upfront before they'll send a replacement out. Unfortunately, for me the GTX 1080 FTW is almost always out of stock on their website, which is why I had to wait almost two months to get mine in the first place.
I am still awaiting confirmation of when my card is going to be sent.