I solved the issue and this is how.
After lot of research and dozens of suggestions I decided to try something simple first.
My Samsung UE39F5500 was connected directly to the Internet, no cables apart from the power.
I opened the back of the TV and made sure everything was properly connected especially the highlighted part on the image. (shows how technical I am).
Solved! Go to Solution.
Unfortunately this is not a solution., its temporarly. I went through all of that process before finally realising the screen’s actually defective. The varying nature of the problem makes you think it’s possibly a glitch and not a fault and perhaps your seeing things. The reality is that it is an ‘intermittent’ fault that it is progressive and not going away. It took me months to realise it needed addressing. Two replaced ‘back light’ screens later and already the third screen is showing early signs of failing again. I’m waiting for it fail more permanently before sending it back whilst still remains under guarantee.
I wouldn't wait if I was you as the problem could happen again after you get it fixed and it's out of warranty. I got mine replaced when the issue wouldn't fix itself anymore and it happened a second time with the replacement screen. The second time it happened it was still within the stores guarantee period so they gave me £600 credit towards a new TV.
Thanks Nathanial, Your point is a valid one, as its so inconsistent I'm just trying to be reasonable and waiting to ensure the fault actually re-appears when they test it.
My updated situation is (due to Covid delays) an inspection/repair report was sent by repairer (£697) which John Lewis refused and they have offered my a model the retails at £499 - original pp for mine was £999 (4.5 years ago).
I can also use that credit and pay extra for another model.
Hmmm...they say it's "equivalent" but only has 2x HDMI compared with the 4x I have now.
Worth trying to squeeze more from them?
For sure. I love John Lewis so won't use the word "squeeze" but if you point out the difference why it's not a like for like replacement they'll surely make another offer. The replacement TV they recommend to me and the one I subsequently got had the HDMI ports on the other side of the TV and a short, fixed power cable.
This meant I had to buy new HDMI cables and have the TV remounted on the wall (which wasn't a simple task requiring new holes etc.). John Lewis contributed towards some of the additional costs.