I've searched and searched the internet for answers and apparently there are none. I cannot find a single thread or comment on someone fixing a faulty Nintendo Switch cartridge themselves as a DIY. I cannot even find information as to that Nintendo does themselves to repair physical game cartridges that get sent in. The Nintendo warranty covers the first 90 days of a first party game from purchase. 

The top three games that become faulty from what I have read are as follow in order:

1) Mario Kart 8 Deluxe
2) Splatoon 2
3) The Legend of Zelda: Breath of the Wild

(There was a third party game as an outlier, but it was a single person, so it may have been a one time fluke.)

I have Mario Kart 8 Deluxe for Nintendo Switch. (Second copy of the game that I've owned.) The game cartridge will not read whatsoever 100 times out of 100. Only the MK8D cartridge has this fault; every other game cartridge works, so I know it's not the console's game cartridge reader. The pins looks pristine like any other game cartridge I have. It has to be something to do with the board inside of the physical cartridge. From what I have read, if you open up a game cartridge, there is no way to put it back together; essentially rendering it useless.

Does anyone have any insight at all regarding this topic of faulty game cartridges? I'm no expert or guru with electronics and PCB's, but I know there are a few of them on this forum. I find it incredibly annoying that there are no answeres on the entire worldwide web... 

These carts were designed to be tamper proof. As you said, you have to do irreversible damage to the cart to get to the pcb. And you will most likely not be able to do anything in the way of a repair without cracking it open. I would imagine that these cost Nintendo so little that if you filed a warranty claim, they probably just chuck it and send you a new one

I doubt they would repair these as well. Most likely just send you a new one  

Even if you are already outside of the warranty period it's still worth it to contact them. Sometimes they will extend you a courtesy

What do folks do with all those Pokemon DS Distribution carts that have been snipped at the bottom? I swear I've seen someone on here that attempts repairs at those...

Not sure how you would repair it anyways isn't it basically just a microsd card in there? Send it to Nintendo like others have said, they generally take good care of people.

I fix them. You basically transplant the chip to another board- it's tedious though.

Hey guys, I just wanted to update that the game managed to fix itself... I won't question how or why and just accept the situation as it presents itself. I was bored and attempted to eject and reinsert the game over and over endlessly (again). I didn't keep count how many tries I attempted, but at a certain point, the game just started working. It now reads every single time the cartridge is inserted into the console. Has anyone read about a fix like this in the past? Anyone have any ideas or theories as to how the cartridge could just fix itself like that?

Sounds like some crud got into the pins and then worked back out? I'd maybe put some high % iso alch on the pins and insert/eject several times a few rounds and let dry.