Question Something of a cursed microSD card

I salvaged a microSD card (a SanDisk ExtremePlus) from an NVIDIA Shield, formatted to exFAT, put some files on it, and then something happened to it. The gist of it is that any changes I make to it, literally any changes, do not persist once I eject the card. I can put files on it, the OS reports that more space was taken up, I can open the files from the microSD card and everything seems fine. It's just when the card is ejected it reverts to a previous state. Tried formatting with Windows and it claims there's a problem with formatting. Tried deleting the partition, but it comes right back. Did this on Linux, same results. Ran it through chkdsk as well and it reported no problems. As far as I'm aware, there's no write-protection on microSD cards. And even if it were on, why would it allow me to put stuff on it as if it'll save it?

In any case, has anyone else seen something like this?