I recently bought a 930B soundbar and since arriving in the past week when watching content or playing a game randomly every minute or so the sound volume will change completely from the soundbar making it sound very dull, completely changing the sound in the room. 

It often fixes itself within 10 seconds but keeps happening and has occurred in Netflix, while playing Xbox and on BBC iPlayer. Sometimes it can take several minutes to change back to normal output. 

I've tried playing around enabling / disabling the space fit sound, it happens on all the sound modes. 

I am connected over eArc to an LG C1 TV. I didn't have issues with the Sony soundbar I just replaced.