BRAVIA-KDL-42W655A slows down or restarts after it connects via mesh or mesh is in the same network

[spiruvas]

BRAVIA-KDL-42W655A slows down or restarts after it connects via mesh or mesh is in the same network

I have a TV in a different room. I have extended my internet connection in that room via cable and used a router as mesh. All devices work great, but the Sony Bravia KDL-42W655A. The TV gets very slow when I start the mesh. It does not matter if I connect via WiFi or via cable. 

The main router and the mash are AVM FritzBox 7520.

If I connect the TV with cable directly to the main router and take out the mash, the TV works fine. The problems are when I introduce a mesh.
How can we fix this?

[royabrown2]

@spiruvas 

Have you set the internet-facing Fritz!box as a Mesh Master?

https://en.avm.de/service/knowledge-base/dok/FRITZ-Box-7520/3354_Setting-up-the-FRITZ-Box-as-a-Mesh-...