Yeah, that's what we were doing in the beginning with this rom. I always use gparted to fix sdcard. This time that did not work and before I don't recall it rebooting to bootloader or seeing that message. I don't know that anything was wrong with the sdcard, I actually just swapped it out with a fresh spare. The problem seemed to be strictly internal as after re-flashing everything and booting successfully, I replaced sdcard with first one and it formatted the first partition external and didn't touch the third. Now that I think about it I don't remember if there was a second for android_meta or not. Keep in mind I was partitioning the card and not just formating it. I mainly posted this experience to share the screenshot in case that info may be useful at some point.I have found that the only successful way I 'recovered' an SD card that I had tried to format for adoptable storage was to re-partition in on a PC, using Partition Magic or similar software, then put back in the tablet and format as portable, not adoptable storage.
Also, make sure you are using the correct TWRP as posted in the OP.