They are FAT32, a 64GB Evo+ and a Verbatim 8GB.
I have tried another small no-name FAT32 with the same result.
I also tried the Evo+ with an NTFS partition but that didn't improve anything.
Unfortunately, there is nothing I've found that reliably makes the card show up or not show up. It seems to be luck of the draw.
I doubt "luck of the draw" is a realistic test parameter for you try and make it happen with but that is just how it is. Or at least it seems that's how it is for the other affected uses out there.
What puzzles me is, why it worked OK at first then slowly degenerated to the point of unreliability. It suggests failing hardware but surely these (Realtek?) readers are in millions of computers and would have caused an uproar by now.
I hope you don't cause your tablets to go into this condition because once it starts there is no turning back.
However, if we knew how to actually cause the failure I'd bet it could be fixed.
So if you want to, just keep banging away at booting back and forth from Windows to Android, inserting and removing the card, shutting down, restarting, rebooting, etc.. Eventually you will either fix it or do the other thing, as they say.