Poor 5GHz performance on ArcherC1900 v1
I have two ArcherC1900 v1 units with the new one connected to the old one via LAN cable. The new one has similar performance on the 2.4GHz band as the old one but for the 5GHz band it seems to connect but have almost no data transfer.
My ISP link is a 100Mbit link and on the 5GHz band of the old unit I am getting excellent results (https://www.speedtest.net/result/i/4315730236). For the new unit, the results on the 5GHz band are terrible (https://www.speedtest.net/result/i/4315728901). These tests were conducted within seconds of each other and from within the same room as each router.
I have also tried swapping the routers making the new one the one connected to the Internet and the old one the one connected to the new one via LAN. The results are the same. I did a reset to factory one the new one but the results were still poor. I also tried unscrewing and swapping the three physical antennas but nothing seems to get the 5GHz band on the new one to work well.