Sorry it's been a bit since I replied, but I ended up having issues with my server I've been trying to sort out.
I managed to get one of the 12TB drives added as parity, and that was good and the process completed without issues. I then attempted the parity swap procedure for the remaining 12TB / bad drive following the process linked. This got to about 80% and the server rebooted. I had several other issues with reboots attempting the process again so I finally just removed the second parity drive from the config, and physically removed the failed 10TB data drive & assigned the old 10TB parity to the failed data drive and let the data-rebuild process take over. This completed without issues.
All drives have a green dot, but the rebuilt drive shows "Unmountable: Wrong or no file system" Do I need another reboot, or do I need to format the unmountable disk?
raptor-unraid-diagnostics-20240130-0937.zip