A very inconsistent approach to what defines a fault

I had previously left a 5-star review for the support received from Samsung - that has now been removed. I purchased a Samsung Q60 85" TV from Hirsch's, about 6 months back. Unfortunately, that TV has white clouding on dark backgrounds. The support from Samsung was great - engineers came out, agreed to the fault and Samsung offered me full refund. Hirchs's recommended that I upgrade to the Q70, which I did for a good deal more money. The exact same fault appeared on this model as well. Samsung have sent engineers out three times (two times after I escalated back to Hirsch's) and whilst they agree with the problem to my face, Samsung are telling me that the engineers have found no fault and that I should go to the Ombudsman if I'm not happy, They said they'd confirm that in writing: the first letter was blank with a letter head; the second (issued 3 months later) confirmed that the engineer found no fault (contrary to what I discussed with the engineers). I do not understand why the exact same fault justified a refund on the cheaper model but not on the more expensive. Whilst the diagnostics may not report faults a visual inspection of the picture clearly demonstrates the problem; unless clouding on a dark background is by design on the Q70!?!? I have three other Samsung TVs – purchased over the years – all have performed flawlessly. This recent purchase has been a diabolical experience. I’m still pursuing a solution with Hirsch’s and hope that common sense and goodwill will prevail. I must say that the Hirsch’s rep that I purchased the TV from has been very helpful in trying to resolve this situation.