Deco X20 Backhaul feature not working
I have six Deco X20s (all six say "US/1.26" on their S/N sticker to the right - which I think indicates the hardware version). They are connected exactly like the attached drawing but with 3 of the 5 X20s wired on the far right in a star from the Cisco Ethernet switch I'm using. [Meaning, where the attached drawing shows "Other Deco Units" I have three wired using X20s using Ethernet cables and I have two that are wireless to the Main.]
My problem is, I cannot get the Ethernet Backhaul feature to work. It used to work fine. I could previously view the settings in the App and the three wired ones indicated "Ethernet" (not WiFi) to the Main. Now suddenly with no changes made by me, they all say "Wifi" and all, at very low antenna power levels because they are a long distance from the Main Deco. Maybe a new firmware update has removed or changed how the automatic/"automagic" Backhaul feature enables itself? I wish I could manually tell the three wired devices to always use the Ethernet cable, but this does not seem possible? Maybe if I log in through a Terminal I could do this (I'd need help with the commands)?
I again followed the Backhaul instructions carefully from the tp-link website by first establishing a WiFi connection with all 5 X20s physically near the Main Deco. Then, after WiFi is clearly working close by, I then moved the 5 X20s to their final, distant destination. Yet, even the three wired X20s never use the Ethernet Backhaul. I know that the cables are working and good because I've used them previously for at least one year, and I have both (1) Link lights at both ends (when I sub in devices with such lights), and (2) I (again) tested the cables with a (simple) Ethernet cable tester. What else can I do? I have changed nothing on the switch since it previously worked, such as: I know I have auto loop detection turned off on it.
Help me Obi-wan Kenobi, you're my only hope. : )