Beoplay H5 - Bluetooth earphones

I was given a pair of Bang & Olufsen earphones as a present in March. Initially, they were ideal: the sound is good and the lack of wires is ideal for the gym, etc. I use them with an iPhone 6s.

However, in the last two months they have developed major problems:

• When listening to Apple Music, or many other platforms (podcasts, Google Play), the music will randomly pause.
• Sometimes the tracks will skip forward.
• Occasionally, while listening to one app, another will be opened - e.g. I'll watch TV on my phone with my headphones and suddenly Apple Music will start playing.

I sent the headphones back to B&O for checking, and they say there is no fault in the headphones themselves.

I then tried resetting and restoring my iPhone. This did not work.

I then tried resetting my iPhone and starting it as a new phone. This worked initially (for a few hours) but now the problem is back.

Does anyone have any idea what is going wrong?

Brian