@Solja I am almost inclined to say you have 100Mbit switch somewhere between Main Deco and Satellite Deco. Now that you confirmed your Main Deco is getting 800Mbit from the Internet, you could test...

@Mark_Deco-M9v.2 This is latest firmware they have on UK TP-Link web site, for example:

@Alexandre. Actually, this is how you could still test Deco hardware if you are willing to give it a try: >4) yes i tried another wifi router instead of Main deco unit and other wifi router has good...

@Mark_Deco-M9v.2 This could have been good test, but it requires network configuration to support Deco in AP node. Yours is not, so you can't test it. I noticed your Deco M9 formware is version...

@Mark_Deco-M9v.2 This may help to narrow issue to either Deco hardware or specific Deco software running in Router mode. If in AP mode the issue does not happen, it is TP-Link software or software...

@Solja Deco M5 has 1Gbps Ethernet ports and can do much better than 100Mbps with Ethernet backhaul. I have Satellite Deco M5 wired directly to ISP Gateway, I am getting 300Mbps download speed on...