This issue has been reproduced with both the Pixel XL and Pixel. When covering the top corner of the phone where the camera lens is (there is a small plastic stripe where the Bluetooth antenna is) the Bluetooth audio will cut out. It is VERY reproducible. Putting the phone in your pocket does not affect the audio, but as soon as you put your hand over the phone it will stop transmitting Bluetooth audio. The Blueooth receiver is Belkin receiver and is approximately 5-6 feet from the phone.