AC-5300 only 5Ghz-1 band working

Hi. I purchased a used ac-5300. I had set it up it’s dual wan option with fall back selected. It worked fine for 2 days. Then on the 3rd day, I restarted it and it got stuck with power led and both bands leds on. No wifi option ssid was shown, i connected it directly with ethernet but could not connect to it. Neither was I able to go into the settings. So, i restored using rescue utility. After reset, it’s 5Ghz-2 band wasn’t working. It’s mac address was also missing.

Then I installed...

AC-5300 only 5Ghz-1 band working