My 2-week new AC88U with merlin 380.68_2 (upgraded from a factory reset 380.68) has a very poor wifi download speed of around 1Mbps on both 2.4G and 5G with a iPad Air 2. My home WAN is FTTH 1Gbps and the wifi upload speed reaches around 400M, so I guess that the culprit isn't the WAN. This problem confuses me so much as it renders my wireless network plainly useless. What's wrong with the router? I attached the screenshots of wifi config pages with this post and hope somebody is willing to help. Many thanks in advance.
