I have bought a beosound system with beolab 2500 loudspeakers. I bought it used. The glasplate funktion does´nt seem to Work. I opens, when you get close, but i does' nt quite close, when you turn of the cd player og the system. I don´t think this is normal. When is it supposed to close? If it is a deficiency, how can you fix it or what do i do wrong?