What age is the car it is has been installed in?
Quite a common thing is that if it is quite a new VW and has a quadlock connector (40pin iso) for audio intergration. then it will be more than likely that a wiring harnesses was used for an easy installation, these can sometimes be poorly made and once connected, the terminals can be pushed away from the pins causing an intermittant supply to the control unit - worth checking if so.
Also, if you're going to contact Parrot then ensure that the software on the Mki9200 and on the phone are the latest versions as manufacturers often unknowingly release these devices with bugs and this also often causes problems.
The parrot forums (through the official site) can be of help i have found, it has quite a few topics already discussd in detail, if you have the time to search that is.
hope this helps