i recently upgrade my firmware version from Archer C6(EU)_V3.2_210322 to Archer C6(EU)_V3.20_210513 but after some time i noticed that my router was not connecting to the internet and showing a red light
After checking the mac address(if used custom mac) was getting changed to default mac address automatically.
After factor reset the issue was still there.
Then i downgraded to previous firmware version (C6(EU)_V3.2_210322 ) and it worked
conclusion-there is a bug in firmware version Archer C6(EU)_V3.20_210513