Same problem for me: with the sd inserted I cannot go to recovery and nothing flash but I resolve in this way: prepared for nand installation as described, switch the box on without sd in, went to recovery, put the sd in and then select "install update from ext"
I did that too.went to android recovery with toothpick, choose the zip file from sd ,it installs then when reboot the box ,no display on tv and box gets bricked.cant access android recovery either.i have to use usb too to recover to android .
Sent from my SM-N910G using Tapatalk
didn't read that you tried, hope you will be able to solve.
I will test optical out at my side. You need to give me a few days, more important things than development planned. 