Is this problem back again? https://forum.armbian.com/index.php/topic/690-upgrade-error-with-armbian-500-on-cubieboard2-running-from-nand/
I also experienced problems with the 5.24 (or was it 5.23?) upgrade made during Christmas. It also bricked the system on NAND, but I don't remember what went wrong. I reinstalled from scratch because no supporting tools where available far away from home.
With the right tools to hand it should be possible to recreate the boot files on NAND with the help of the linked thread.
As I have to do the 5.25 upgrade in the next days, I would appreciate when this problem gets sorted out sooner than later...
