I'm really sorry to learn about the problems you're experiencing with your TV service at the moment, it's not what we want for you!
I've had a check on the TV in the office and I'm not seeing a difference in audio between the two channels, did this happen while you were watching a particular game or have you noticed it happens any time you try to watch it?
It was the Celtic v Malmo match. Also noticed it with the Man Utd match. I've currently got it on BT Sports 2HD and the same thing is happening with the Celtic v Dundee Utd match. It looks to be happening whenever there is a live broadcast.