@SrDarkWarrior 

I did that, and there is something really really strange !!! I will give two examples:

1. I have the main deco called Office, the printer is located 30 cm from it on the same desk and the printer is connected, according to the deco app to the slave deco called Living which is downstairs on floor 1

2. The second deco slave is in the 1st floor called living room and its located under my TV. Around my TV I setup a strip light and on the deco app it says it connected to Playroom deco which is the 3rd deco on the other side of my house.

I have more examples, so I dont understand how they do this, maybe this is the reason they removed these features from V2 cause they are not working as they should.

each device should be connected to the nearest deco and it doesnt look like it !!!  

Network topology and device names seems to look strange on most type of routers

Regarding ps4 i assume you have changed the connection settings in the ps4. If you were on wifi before it will not automatically switch to wired just because you connected the eth cable

@e3henri 

Leave PS4

what about these devices?

1. I have the main deco called Office, the printer is located 30 cm from it on the same desk and the printer is connected, according to the deco app to the slave deco called Living which is downstairs on floor 1

2. The second deco slave is in the 1st floor called living room and its located under my TV. Around my TV I setup a strip light and on the deco app it says it connected to Playroom deco which is the 3rd deco on the other side of my house.

@avniel 

I don't have all those issues and more than 20 devices connected. I suggest you use an app on Android like Fing to check ip addresses and Mac addresses of your Deco's and then check the physical Deco's and Deco app if you not accidentally named them wrongly

Or more easily. Just disconnect one Deco and see if this is the one you expected using the app

@Koeno 

I'm using Fing for a long time. 

I will check the names but I doubt that this the issue because I named them when I set each one and place it, so I guess it won't be the issue. 

@avniel 

Just keep in mind that if you use mesh it means that it is not necessary the nearest Deco but the one who should have the best connection. In many cases this will be the nearest Deco but not always. For instance if the signal and bandwidth to the main Deco is very strong, a device may connect directly to the main instead of the nearest. I guess it is a complicated algorithm because it depends on many factors.

@Koeno 

checked on my network (24 devices) and also seems okay - devices are connected to the deco that seems the most logical. 
 

Even the robot vacuum; this one switches from one deco to another while cleaning trough the house. 

@Koeno 

Yeah, I know and maybe that is the case

@Robert_M 

Do you see it live switch between decos? 

@e3henri 

Does anyone use 4 decos of m9 plus?

Will it work ok to use 3 pack of m9 plus and one more m5 in the same network ?