@Axel59 

Hey Axel

The M4 Mesh uses a 5Ghz backhaul to connect the devices, you mentioned that internet is 500mbps coming into the network, honestly I don't think the M4 is powerful enough for your internet connection.

Based on my experience M4 stations will have around 500mbps connections between eachother in a normal setting, add a few connected device and this will drop to ~300mbps which is perfectly acceptable for VDSL internet but not the 500mbps internet you have.   This I believe is what is happening to you with the 250mbps limit.

I would recommend upgrading to at least the P9 model, ideally the X60 WiFi 6 would be better for you

For the record I had the same problem, I went from VDSL 80mbps to FTTP 900 and it was crippled by my internal networking.  I found the best solution was Omada SDN Router, Switch, Controller and Access Point, it was the best most reliable way to handle the faster internet speeds.

Hope that helps

@Philbert Thx for your feedback,

I have 500mbps with my last router in wifi AC1200, my internet connection is up to 10go/s (look the screen).
Ok I go to buy the X60.
If i adding a P9 in first with my M4, that won't change?

hello @TP-Link 

I have the same trouble @Axel59 has. The speed of the devices connected to an "slave" node is not as fast as I expected it was going to be. 

I thought this kit would let me keep a fast wifi along all the house. It's a pity.