Pioneer DEH-P7000BT and Iphone 5

I have a Pioneer DEH-P7000BT Receiver and I have been using with my old Iphone 4 with no any complaint. Now I switched to Iphone 5 and, no matter I can connect to the Receiver via Bluetooth with no any issue, suddenly the sound becomes noisy until I disconnect the Bluetooht and connect again. Seems to be a problem about a loosing of sincronizing or something similar.

Anyone knows this issue and how to solve it ?