Sorry this is a foreign language to me. It's a socket in the wall that's fibre. Thats wher the router is connected to
Does it look like this.
Or like this
Was it an engineer install? If so is it possible the engineer swapped the sockets so the socket you are using is now actually the master socket?
Basically it was a sub-contractor ordered by but not bt branded.
I don't think he changed the master socket, he asked me which one i wanted the new socket in and the kitchen was more convinient. He was in and out within 15 minutes and he didn't do anything to the master socket.
That could be your problem. If it had been an openreach engineer then he would have swapped the sockets about
i would try try the other socket and see if connection improves