I've had 3 Deco x50 connected to BT smart hub 2 for a number of years but I have never been confident that the Ethernet backhaul has been working correctly

I have Deco setup as a Access Point, it is connected to the BT smart hub 2 via ethernet cable, or at least it should be, the other two Decos are also connected via ethernet cables directly to the smart hub. 

However looking at the Deco app, it doesn't seem to be connecting to all 3 devices via ethernet.

Kitchen is the main Deco with "main bedroom" and "bedroom" being satellites .  I have swapped the hub ports the cables for Kitchen and bedroom around, for a few moments it shows Kitchen central, with thw two bedrooms on either side but then it reverts to how it was before, even through they are using different ports.

I've just managed to get into the BT Smarthub settings and found connected devices tab and it appears Kitchen and Bedroom Deco units are connected via the ethernet ports, with the main bedroom Deco connect via the Kitchen Deco .

So to me it appears the app network picture is wrong, is it? and I may have a problem with the ethernet cable to main bedroom