OK. Here as promised, the situation with this Live Control knob screen pop up issue which I'm pleased to say has been resolved. However the cause is unknown. So the keyboard is being sent back to Yamaha for analysis.
Yamaha have now agreed that there IS an issue here. I sent them, amongst other information including videos of my own SX700, the Youtube Video from Bonners (see earlier in the thread) which clearly shows this fault existed back in 2019!! on a brand new SX900 which they had just un boxed and were demonstrating and not picked up on, and several photos. So it IS an issue that's been there right from the launch of the SX700 and SX900.
Having now convinced them that this IS a genuine problem, and after consultation with the dealer, Yamaha are going to replace this keyboard with a Brand New keyboard.
So at this moment in time, I'm glad that they have seen sense on it, and it solves my problem, but to be clear, none of us, The dealer, Yamaha, or myself currently have a clue what is causing this anomaly. If I DO find out, I'll post.........
Keith.