#PSA if you have European copies for Pokémon Omega Ruby/Alpha Sapphire: there have been numerous reports from ResetEra and Twitter. This has been caused by the FlashROM chip, which some other games have (I can’t find a definitive list of those atm, sorry)
It’s impossible to check if this is super widespread, but it can’t hurt to check.
My Alpha Sapphire copy still works, thankfully.
Now I’m not as pro-corporate and stuck up than other Pokémon website admins so I’m going to tell you this: I highly encourage, if you have a minimum of tech-savvyness (it’s mostly moving files around and carefully following instructions), please hack your 3DS with this guide : https://3ds.hacks.guide/
It will allow you to install homebrew apps to your 3DS such as Checkpoint, which allows you to back up and restore save data from cartridges and installed games, like I just did with my SA cart.
@Siphonay is it just OS/AS or the other 3ds games too like x and y?
@MochiWaifu It’s any game that uses FlashROM chips, like the US release of Persona Q. I wouldn’t be able to tell which games actually use those
@MochiWaifu @Siphonay doesn't hurt to have backups of ROMs and save files, and 3DS homebrew is some of the best out there