I'm trying to remove my RNS-E head unit to get access to the aerial cable. I've inserted the two keys that i used to use for the Concert 2 on my old car, and have hit problems. Firstly, the unit won't come out. Secondly, the keys now won't come out. Thirdly, the left hand key appears to be interfering with the radio function button. I can select the radio function, but the button seems to be sticking slightly, and the four control buttons aren't responding in radio mode. Please can someone help me?