My 3DS SD card keeps deleting files and FBI fails to install apps

Hi everyone, I’m having a big issue with my modded 3DS.

Whenever I put files on my SD card, they just disappear automatically after I eject and reinsert the card, or after I try to use them. On top of that, when I try to download/install files through FBI, the download always fails, and then all of my apps disappear from the home menu until I reboot.

I already tried moving files again, but nothing sticks. It feels like the SD card is either corrupted or not being recognized properly.

Has anyone experienced this before? Do you think it’s a fake/broken SD card issue, or could it be something else with my setup? Any advice would be really appreciated!

Thanks in advance.