Bluetooth hardware defect?

Hi all. I've recently bought a new pair of Bluetooth earphones and have been trying to use them on my iPhone 6 (now running 9.3 but I was using them under 9.2 as well). I repeatedly lose the right audio channel while listening to music via Spotify or the native music player. It generally starts about five minutes after turning music on and gets progressively worse until the right channel drops altogether. Left channel appears unaffected. I've used the same headphones on a different iPhone (also a 6, running 9.2.1) and there is no drop-out. So I'm convinced this is a Bluetooth hardware issue in the phone. Does anyone have any other possible solutions, or if not, is the BT chip something that can be swapped out?

Thanks

Ed.