Shield TV 2015 rebooted during system.img flashing

Hi guys,

previous version 6.0.0, upgrading to 7.0.1. blob, boot and recovery images flashed fine. Board rebooted without a reason while flashing system.img. Now there is no video output and I am unable to enter fastboot. The question is what are the other methods of partitioning built-in NAND?

Regards,
M.