That arrangement is known as "star wiring". It's not a great problem for normal phones, but it can ruin broadband speed.
You could pay Openreach to sort it out (arranged through BT).
Alternatively, if you can work out which socket is supposed to be the master, you could disconnect all the others at the junction box and see if that helps. You would then need to re-wire any extensions that you need so that they are connected to the back of the master socket.
But ideally, you want a proper new NTE5 master socket, from Openreach.
We live in a Victorian house and when moved in the phone sockets were so bad it could not handle upto 1mb. We paid £150 odd quid and I stripped out the old sockets etc... BTOR came the next day and ran a new line from the pole to the desired location. I fitted some extensions later on - definitely worth it as speeds shot up to 10 - 15mb after that. Apparently a lot of the cables corroded away due to damp and oldness. We now have BT infinity and speeds of 50 - 55 mb so it would be definitely worth it if your cables are old.