Ouch. Thanks for the information. I too had the UX581 and I loved it. I had purchased it at the Microsoft Store. I purchased the Microsoft Complete insurance that also covers accidental damage. Two months ago I developed a horizontal line across the center of the screen. I sent it in for repair and they sent me back a check for my original purchase price of $2,999.00 telling me it was not repairable. This time I have ordered the UX582 from Amazon, but delivery estimate is several weeks out.
I will carefully check the screens out when I receive the UX582. I've been with Amazon for over 20 years and Prime since inception. I have never had a problem returning anything. I'll search YouTube for the 5% gray test.
Where did you purchase yours? Will you try again?