I have 2007 MC with the Aux In. There must be a loose connection with the plug as it sounds like you're missing half the frequencies unless you spin the 3.55 mm cable just right. Travelling over bumpy roads renders that solution useless.

I've been searching for a way to take it apart but am not sure if someone went through the same process? I searched but could not find a solution or method to replace. Hoping I can DIY fix.

Thanks!