It seems the 1.4.3 update zip from B&N isn't suitable as a factory.zip
neither the signed or unsigned works
I've grabbed 2 factory zips from other units
1.2.0 and 1.3.0 and copied them into factory, and they both work as expected on the 8 failed boots
I didn't get the complete result that I wanted , but good enough.
Thanks again for your help leapinlar, It's appreciated.