I have a 1997 M3. The factory-installed radio light died about a year ago, but the reception was still good. Over time, the reception became flaky: Good reception for a few minutes, then reception mixed with static for a few minutes, then several minutes of total silence. I bought an aftermarket 1997 M3 radio and installed it. The radio lights works and I can control the speakers, but I get only static (and barely one or two FM stations.) What's going on?