Why doesn't supervisor log the output of a child process?

When I run the script server.sh (runs a quake dedicated server) in the terminal it will create initialization output like

And when some person connects to the server then this script will output something like Person xyz has connected

I want supervisor to manage this server.sh script but supervisor does not output any kind of initialization messages or connecting message (if someone connects).
Stdout and stderr are both logged. Why does supervisor not log the output of server.sh?

Here is my supervisord.conf

EDIT:
I noticed a strange behaviour of server.sh

generates no output in out.txt (no Game initialization, nothink). But only after i typed in stdin "quit" (server.sh quits now) then the Game initialization and so on got written into file out.txt