God Mode MicroSD Card

I have a SanDisk 64GB MicroSD card that I have used for about 8 months without any issue. Recently the SD card would write data, then the data would disappear. This was extremely frustrating after trying to backup phone data to make a switch and realizing that, even though I verified the existence of the backed up data including opening specific files, that when I put it into a different phone, the data was gone. Everything that was there before this started happening won't go away. I have deleted everything on the card multiple times and it keeps coming back.

I can't get the card to format for the life of me. I run a format through cmd and the card still returns to life as it's old self with all the data that doesn't wipe still fully accessible and usable. Now the thing is I can't format through any program besides cmd. In cmd I get a notice before I format that the card needs to be forced to dismount ("Volume is in use by another process"). I think the card is perma-stuck mounted to my old phone. No matter what I do nothing succeeds and I'm really at a loss. There's no write protection switch on the card and I don't know what I need to do to fix the issue. I'd really like this card back and not have to burn it (I mean that literally) and spend $50 for a new one.

Any help would be greatly appreciated.