Why did you automatically assume the fault was with the Deco? The fault was with the Ring: https://community.ring.com/t5/Video-Doorbells/TP-Link-Deco-Mesh-WiFi-bricking-Ring-cameras/td-p/460/page/11

Please rephrase your question (questions?) - a >100 word sentence does not make it easy to answer.

This is the wrong forum. https://community.tp-link.com/en/home/forum/81

Have you tried swapping 2 and 3? Or resetting 3 and setting it up again. Yes, this system really needs an Ethernet backhaul indicator/test.

There's no reason either configuration wouldn't work. I'm running all Deco's in AP/Ethernet mode back to a Netgear switch and it works brilliantly. I don't know why it would be slow as it is, unless...

If only I'd read this thread earlier... I just connected my Deco's to a D-Link DGS-1008A and it broke my whole network. Luckily I had a spare Netgear GS105 which works beautifully. TP-Link (and...