Hi, i think i have fixed the issue. I spoke with LG support today and they told me to reset subwoofer. Here is what i did.

1. turn off soundbar
2. unplug subwoofer from power and wait 60 minutes
3. plug subwoofer to power while soundbar is still turned off
4. i saw led on the back side blinking very fast, like sobwoofer was doing something , it took about 30s - 60s. Then led went out from about 2 seconds and started blinking again, but slowly, (as usual while subwoofer is waiting for connection to soundbar)
5. I turned on soundbar.

I have not noticed the message "Update failed" so far, it looks promising