RT-AC66U is using firmware 18.104.22.168.354 (main floor of house). USB-AC53 (second floor of house) is connecting to channel 149. Full signal bars are showing. Wireless mode is N only. Channel bandwidth is 80 Mhz Tx Power is 120 mW. Initially the USB-AC53 connects at 527 Mbps, and stays that way all day. I hibernate my system, and the next day, the USB-AC53 connects at 176 Mbps. Disconnecting and reconnecting to AC SSID doesn't help. I need to reset the RT-AC66U to reconnect at 527 Mbps. Is this a firmware bug?