I assume you mean by "remove power" simply switch off rather than unplug?
OK, I did that but it hasn't solved the problem.
It does when on the TV channel but not when on the HMDI (Human-Rec) channel which I usually stay on.
Have gone through that process. At the end of it, it confirmed that display was 16.9. But it is still coming up 14.9.
Another point of note is this. It used to be that the sound was at a higher volume on the Humaz-Rec channel than on the TV channel. That now seems to have reversed.