First things first, this is not really a topic for Test equipment category.
It's about salesmen and buyers..
Second, discussion is going in wrong direction because not everybody read ALL posts from OP, it seems to me.
First he made bombastic title and wrote " My BRAND NEW DSOX3014A is defective and Keysight doesn't want to honor the warranty."
Then he mentions that scope is 8 years old. It is so old that, in fact, it has AGILENT on the front.
Reading through this it looks like OP was under impression that he bought BRAND NEW scope and was given 8 years old NOS equipment, and now nor vendor nor Keysight want to help him.
Several posts later he reveals that he has paid for the scope only 2000 USD (in a Brazil that is usually much more expensive than in USA) and that he knew it was NOS and and knew the price was so good because of that. Also vendor was, once upon a time, Agilent partner but it's not anymore, so they can't solve this trough official channels. But he expected full warranty.
Bad thing he didn't verify first.
While I sympathise with his situation, Keysight is not really bound to help him and give him warranty. It came from unofficial channel, and is NOS.
Honest thing is for a vendor to honor warranty and pay for repairs.
Which they don't want to do...
But hey, one can try then, maybe Keysight will do something about, because they are known to help sometimes if you ask nicely and if it's a nice story. They get some good will and publicity and they help someone... It's all good.
So now problems.
First this is a wrong way to ask. It's nice to be nice. You don't attack and then ask for help.
Second, scope might have some problem, but more likely it's a self cal thing.
So you try that first and then if that doesn't work, you ask for help.
But no, OP's first reaction was to try to send it for repair (which today means new mainboard or whatnot), because he is appalled that his "brand new" scope is not perfect as it should be. While he damn well knows it is NOS, and that because of that he paid half the price (maybe even less in Brazil) of the really new one.
It's a peculiar story...
It might be that he is fishing for things he didn't pay for.
Or it might be he's an nice honorable man that gave his last penny and now is desperate it all worked out so anticlimactically.
I don't know, don't know the man. I won't judge.
But there are few things that can be done.
1. Try Self cal. If it works, false alarm. All are happy. And then, as soon as possible put newest firmware on it before he loses FLASH. Those are THE original sinners..
2. If it's still bad after self cal, he can apologize to Keysight for attacking them and ask for help. Nicely. Maybe they can forfeit diagnostic fee. Maybe they will chose to honor warranty.
But this was better solved with PM to Daniel.
3. Can he purchase extended warranty? Usually you can, for comparatively little money. Again, work with Keysight.
4. If all fails, pay for the repair. In the end, you might still end up cheaper than buying a new one at full retail price...
But as a first step, change the title. They didn't refuse your warranty. You bought your scope in a way that didn't give you any warranty. Your beef is with vendor. And you attacked only people that can help you..
Flies, honey and vinegar...