Ok for those keeping up with my story over the last couple of pages of this thread, I have an update.
Challenged with finding a suitable replacement for my XE90 that seems to have an inherent vertical banding issue (probably only noticeable to compulsive nerds like me...), I went to the store today to see what I can get for my £2500 store credit. It turns out finding a replacement is not as simple as I thought. I know they say there isn't such thing as a perfect TV but my word, why is it that every model seems to have some annoying issue?
Samsung MU9000 - Still has the annoying HDR game mode bug
Panasonic EX750 - Nits way too low for good HDR performance
LG SJ850V - IPS panel with horrible contrast
SONY XE90 - As the issue I have been experiencing seems to be a general model issue there is so no point getting another one
These were the only options in my price range really and as I am tied to the store, no other models are eligible. Anyway, I spent a good hour in the store and walked out with nothing.
Deflated, I went home to chew things over. I was tempted just to buy the cheapest Hisense TV, take a hit with quality but at least I wouldn't be spending a fortune.
But after some careful thought I decided to give Sony one last go. But this time with the XE9305 which has conveniently come down in price since this fiasco of mine began about 2 months ago.
I am hopeful it will have a different panel design than the XE90 so I don't get the same issue. But to be honest, if it does I am at the point where it doesn't matter. I hate dropping £2.5k on a product that has an issue but it may well be the better of all the evils and at least I will have a nice set (that has Dolby Vision as well - bonus).
Delivery in two weeks. Fingers crossed...