Car radio stops playing?

A while ago I had best buy install a radio for me that I had. Everything went fine and music plays. But after couple of seconds my electric antenna on the car goes back down, the music stops playing but there's an equalizer on the radio and it shows it as playing, This happens with cd, the aux, and radio. Best buy told me i have a blown speaker and need to replace it. I know for a fact that its not, because when the weathers nice like hot, that's the only time when this happens. All winter long when it was cold it never stopped playing and worked fine, until the weather got better and it only works for like max of 30 seconds. What is the problem? Is the radio the problem? and since i get a lifetime warranty for the installation from best buy, can i buy a new radio and have them install it for free? thank you.