dockerized minimal multiplayer game renders almost black

Using UE 5.4.4, I created a minimal multiplayer game sample. One or many characters on a bare default level floor. The game also contains the pixel streaming plugin. I put the server, the client and the streamer on a docker-compose setup.

In the client-server-streamer configuration, the single (or more) character streaming image (On Firefox for instance) is very very dark but not completely black. I can see the outline of the character with a thin shading around the lines. If I make the character walk/run forward, I can not make him stop, nor go backward to the best of what I can see.

However, if I just put the pixel streamer and a standalone client on a docker-compose set up. (I removed the server service and the dependence of the client on the server) then the only client streamed image renders as expected. Sky, clouds, floor and character are fully visible with a proper lighting. I have full control over the character’s movement, forward, backward change direction and stop.

My question is what did I miss when producing the server package to get such a broken (multi)player setup with a server? Could it be some incorrect configuration?

In case this can be a hint to anyone reading this post:

After reducing the scope of the problem, I confirm the issue occurs also on the same minimal game but without the pixel streaming plugin and without containerization. It appears on both Windows and Linux.