Hey everyone!

I have a couple of Deco x60 v3.2, in access-point mode, that are refusing to work with ethernet backhaul when connected to the ethernet ports of an AX72 Pro router with wifi disabled.

The topology looks like this:

               ISP Fiber Converter

                            |

          Tp-Link AX72 Pro Router

                 |                             |

      Deco1(main)         Deco2

The General questions about Ethernet Backhaul mention that "When the Deco is set to work under Access Point mode, you can wire satellite Deco to any Deco unit or the main modem/router.", so I don't see anything wrong in my setup.

I would rather avoid buying another switch as the 4 ethernet ports in the router are all that I need.

The behavior when I connect the satellite deco (deco2) to ethernet is that once every minute or so, the status led switches from green to red (for about 10-20 seconds) and then back to green. In the app, the satellite shows as connected to wireless not to ethernet.

What I tried:

1. Tested the ethernet connections between the router and the end of the cable where the Decos are connecting, with a laptop. Everything looks good. This ruled out the Ethernet cabling.
2. I switched to Deco2 as main, while leaving everything else the same. Deco2 worked fine, it had internet connection, but the bad behavior moved to Deco1 (statis led green-red-green, showed as connected to wifi). This again ruled out the ethernet cabling.
3. Connected the satellite deco1 with a short cable to deco2. This worked fine. Status led solid green and deco2 showed as connected to ethernet in the app. This seems to rule out an issue with the Decos and seems to indicate that the LAN ports in the AX72 Pro router are the issue. 
4. The router doesn't have any network loop detection options for lan. It only has RX/TX flow control switches. I tried disabling those but the situation stayed the same.

Anything else I can try? 

Thank you