My BT Quad Studio 3100 makes bleaping noises?

My BT Quad Studio 3100 makes bleaping noises when the handsets are resting on the chargers. It is usally just the one, but never all four together. It is not always the same one and I am not sure if it is stopping calls from coming in. Also, when the phone rings, sometimes the noise is not the normal 'ring ring' sound, but a continuous ring, until you pick it up.
Can either of these faultsbe corrected or it is terminal please?