U-Boot for Zyxel NSA-325v2 kwboot didn't help (3 replies)

Hi,
There is no stock uboot or doesn't start. I don't know history of this hardware.
Is it hardware issue or I can try something else:

/kwboot-tool# kwboot -t -B 115200 /dev/ttyUSB0 -b uboot.2017.07-tld-1.nsa325.mtd0.kwb -p 
Sending boot message. Please reboot the target...\
Sending boot image...
  0 % [......................................................................]
  1 % [......................................................................]
  3 % [......................................................................]
 95 % [......................................................................]
 97 % [......................................................................]
 99 % [....................................]
[Type Ctrl-\ + c to quit]
?

I have second nsa325v2 and it is working fine. Does it mean that this is hardware issue ? Is there any thing else I can try ?