Console has YLOD (bricked apparently) regardless of whether NOR Tristate is grounded? This indicates a hardware fault (not related to the flash)
Program the original backup flash (that was working) then read it back onto the SD card - compare the 2 files with hexeditor - any differences mean the backup isn't being written properly which takes us back to the clip seating.
I personally repair consoles and have done for some time - a reflow will fix a lot of consoles if:
a) its done properly with the right equipment (not a hot air gun or in the oven...)
b) if the console hasn't been mauled by a previous "modder" or owner
Yes reballing the console is a sure way to repair it but no need to throw YLOD's in the bin. People still buy them don't you know?