OK, I'm not entirely sure what's going on here; are you saying that the extensions are terminated in jack plugs? What I'd say is that the socket next to the TV has issues. Probably a defective cable run.
As has already been said, the connection is only guaranteed up to the master, so a rewire of this extension would cost you.
That said, it's not a difficult job to do yourself:
http://www.wppltd.demon.co.uk/WPP/Wi...telephone.html