I'm here Sergio...
Ok your FM Modulator is transmitting on a frequency that is being used by a radio tower somewhere near your current location..
If you will direct your attention to your remote control.
Directly under the RED power button there is a button labeled DVD -A-
Please press that button one time. (This will designate the remote only to work on the MONITOR -A- (Your Drivers side headrest monitor)
Directly under that DVD -A- button there is another button labeled Sound Around ON/OFF Please press that button and make sure that your FM Mod is transmitting (It will read in green on the screen FM MOD CH1 88.3)
On the remote directly 2 bottons to the right of the Sound Around ON/OFF button there is a button labeled Sound Around Select
That button will change the frequency that the system transmits on from 88.3,88.5,88.7,88.9,90.5 and so on. After you change the frequency that the system is transmitting on, please change the radio station on your X5's radio to match the station displayed on the -A- Monitor in green and you should have a clearer signal.
YOur system is functioning properly keep in mind it is only FM modulation and because of your demogrphical location signal might fade in and fade out if you come close to a Radio Tower the is broadcasting 50,000 watts of funk from a radio station. The headphones however are IR and will never fade in or out, but I realize that my very discriminating judges are to small for headphones at their ages. Please contact me on my cel or at the office if you need additional help. Thanks Sergio!
Peace out!