When I watch SkyOne, the sound keeps flipping over to the sound from Duke+1 after a few seconds - and staying there. (Watching the ABs with a tennis commentary this morning was both surreal & frustrating. Fortunately, my daughter had access to a  Sky online account).

I tried rebooting, including disconnecting from the power.

I've noticed this before when channel-grazing but, because I wasn't wanting to watch anything on Prime (as it was then) at that time, didn't make the time to look into the issue then.