Changing the transmit power to middle seems to do the trick on mine, Archer C5 1200 US V2.

@Kevin_Z Confirmed the label is US v2.0. thanks

I installed the beta firmware for Ac1200 V2 US but I keep getting an error on any browsers that I used. Error message: NET::ERR_CERT_AUTHORITY_INVALID in Opera and something about "Product RooT CA"...