Hi, not the original posters, but it's happening to me too. At random, for minutes at a time, the mute function flips itself on and off. Doesn't seem to matter if it's in an input or not, happens on main menu. I not only tried taking the batteries out of the remote, I found it isn't the remote found it at all. You can use a phone camera to see the light in the remote activate when pressing buttons, and I've verified when the tv is muting itself, the remote is not activating.
I just finished a 'factory reset' on the tv itself and the problem was happening during setup.
Ideas?