Door Locks and SatNav Issue

Hi this is my first post , I have had my 02 Range Rover Vogue since January and a few months my door handle cable snapped on the drivers door , I purchased one and replaced it but the central locking wouldn't open/close this door, but was fine using the normal key and all the rest were opening and closing with the key . A few weeks back the back passenger stopped opening and closing with the key as well and we have to open the door from the inside . Does anyone have any ideas , I have tried resetting the keys but this doesn't appear to make any difference . I have also had another problem which is the sat/nav stereo is switching itself off and on , sometimes no screen with sound , sometimes nothing at all and sometimes the screen comes on a different colour with no sound .

Thanks Neil