I believe the information advised to Halfords was if the observations are the same regardless of the audio source, there may be insufficient power supply going into the Parrot MKi9200 when the music is streaming at higher volume.
I advise you request Halfords to contact their technical support line again if they are still having difficulties.
If you have installed this yourself, I recommend to contact technical directly. If you are from outside of the UK/Ireland, please contact the technical support for your country, if you are unsure, E mail the team from the online form at: http://www.parrot.com/uk/support/techni … ntact_form
However, this topic will remain open in order to allow members of the forum to also assist you.
Parrot Advisor UK 3
Parrot UK & Ireland
E mail: http://www.parrot.com/uk/support/hotline/
0121 359 2380