Call for an experiment
If you have a screen in a car manufactured before April 2019, and have not yet incurred the yellow border issue - you have a chance to run an experiment that might save a lot of fellow Tesla owners money and time. Take a piece of opaque black paper - and simply tape it to an area on the left or right of your screen. It should be about 3 inches wide, and at least three inches tall. It should aligned to touch either the left or right border of the screen. Leave that piece of paper in place until the yellowing occurs. Then remove the paper and report whether the yellowing occurred under the piece of paper. If the yellowing occurs under the paper, then the issue is very likely not caused by sunlight.
Any takers?
Wildag, I haven't gotten the outcome of my arbitration case yet, but -- I will say that Ryan said he "didn't mention anything about sunlight" during my case. He almost seemed offended that I would insinuate such a thing. Their tactics (his tactics) change depending on the person and the case. Not good.
My IC is also yellowing, (and YES it is the same nature as the MCU) and it is following the contour of the inner bezel, all the way around. Sunlight never gets here - especially at the top of the IC bezel. (The sun would have to shine from below the seat.) Sunlight is not causing this yellowing. Additionally my MCU yellowing started under the upper bezel of the MCU. This area does not get more sunlight than the rest of the display, it gets less.
But Tesla adapts their 'cause' depending on the case. Ryan is dishonest and will lie to win, and he knows that, and has no problem with it. (Perhaps he is behind his unyellowed computer screen right now acting faux-offended, or perhaps he's kicking back with a beer laughing to himself about how many customers he screwed over. Congrats, Ryan. You're a wonderful human being. I wonder what car you drive. Bet it's not a Tesla.)
I've been looking at this technically, and I've done some experiments -- I do not believe this is caused by sunlight either. I believe it is caused by uncured adhesive and oxidization. UV further cures the adhesive. Note that the Tesla's windows filter UV pretty effectively, so in a way, sunlight may help this situation, not cause it.
Many, many, (MOST) industrial adhesives are UV-cured.
If Tesla does apply the front glass, not Innolux, it may have been something as simple and stupid as Tesla not allowing the adhesives to UV-cure long enough before installing them, opening up uncured adhesive to the possibility of oxidization.
Note that even on the fixed screens, if you apply a UV light to them, the previous band will be visible under UV light. So the UV application does indeed seem to clear the yellowing somewhat in the visible spectrum, but viewing the display under UV again shows that after the 'fix' there's certainly still some damage/degradation/anomaly that's still there.
What this means for fix longevity, I don't know.