@randomxan Your screenshot from that test is not shown in reply, so I haven't seen it. It is possible you configured bandwidth management features in Deco, such as priority devices, or they were...

@randomxan I can tell from screenshot you provided that your Satellite Deco is properly placed. It has good link to Main Deco. That means, your Satellite Deco delivers the best speed it can at your...

@randomxan Your Satellite Deco behaves as an intelligent WiFi range extender. Google for "wifi range extender cuts bandwidth by half" to see an explanation why Satellite Deco cuts speed in half. The...

@KingPing I believe this message appears when M5 negotiates 100Mbps Ethernet link instead of gigabit. Modern networking equipment is often gigabit or more, so having 100Mbps might point at Ethernet...

@KingPing It is possible TP-Link started to use new MAC address prefix, and it is unknown to that app. Google for web sites offering "MAC address vendor lookup" and try M5 MAC address through them....

@Loco9 If Deco app shows low signal for Satellite unit, you must move that unit closer to Main Deco. I am assuming you are talking about low signal from Show List screen in Deco app, such as: