Originally Posted by Ken@BSW

Are these vehicles with poor FM reception previously-owned vehicles by chance? If so, I would check the entire length of the antenna cable to make sure nobody had done any 'modification', epossibly for added FM modulated devices, etc. Somebody could have possibly left an FM modulator plugged in for all you might know.

As for checking the antenna connections themselves, the FM antenna amplifier is located above the drivers side rear wheel well. Unfortunately, in order to get to it to check the connections there, half the rear of the vehicle needs to come apart, but it could very well be a source of these issues. Hope this helps. If it does, please keep me posted, so I can give the advice for others here and on other forums at a later date. Sorry guys, but if some of the idea's work, I can't keep it just an X5World secret