I use a bluetooth headset all the time and sound playback can cut out if the phone is too far away from the headset, or if arms / clothing get in the way of the signal. I tend to keep the phone in my breast pocket and that's OK. In the trouser pocket, it's terrible.
So try putting the phone nearer to your headset and see if that makes any difference.
Bluetooth radio is very, very low power, and it's not surprising the signal can get cut off by objects that are in the way. Distance is a big factor too. I guess some headsets are better at receiving a reduced signal than others.