Wow people...
https://gbatemp.net/threads/retroarch-switch.492920/
Using an SD formatted as exFat is NOT officially supported.
If you are using RetroArch on Switch, FAT32 is the recommended and only way supported officially by the team.
Any questions related to exFat or file corruption might be ignored.
Using Retroarch with exFat is asking for trouble, whether you're a noob or not. Retroarch is almost constantly reading & writing from files, and I know the key with Homebrew is to always "properly" exit and not use the Home button, especially during writes, but if your console locks up (which is not uncommon, especially if you're playing with settings on some cores) you could be SOL.
Use FAT32. You can still install large NSPs over USB, over the network, or you can use an NSP Splitter. Tinfoil makes it easy if you're using certain "shops." Otherwise, USB installs are great, they save you time because you don't need to copy the NSP to the SD card first. There's really no reason to stick with exFat.
Chances are that your emuMMC is fine, you just need to follow the same directions other people are telling you. Reformat your card, copy over new versions of SX OS, Retroarch, and whatever else you want. But for god's sake, format it as FAT32, not exFat!
And for the record, I used to use exFat, and the only time I saw corruption was after using Retroarch. Screwed up my card pretty bad, even filenames had illegible characters in them. Switched to FAT32 and have never had a problem since.
