Yellowing was there before, just before it wasn't as easy to see as it now.
Question. Once replaced is there a warranty on the replacement part?
Example: Car is at 49,999 and screen get replaced and yellows 6 months later.
Some car manufacturers provide a warranty on a repair while others provide a warranty on a part replaced out of warranty. Like 6 months x miles.....
I had a conversation with a service advisor about this exact question on Monday as my car was in for the end of warranty inspection (79,000km).
Basically, they will try and adopt a reasonable stance. If your car is past its warranty but a previous job under warranty goes bad, depending on usage (read mileage count) post-warranty, they would possibly still cover it under goodwill.
My example: I got my MCU/Screen replaced at 60,000km in July. Say my screen goes bad again at 90,000km I should legitimately expect they would replace it again under goodwill. That however might be my last replacement, but not necessarily, depending on how the replacement screen behaves. Replacement parts all have subsequent 20,000km warranty of their own. So If you replace your screen at 49,999km your new screen is covered by its own warranty now for another what 12k miles?
But this is Tesla service and barring exceptions, Tesla generally has our backs. This is why we do business with them right?
This doesn't mean however you shouldn't be prepared to argue in order to win your point if you ask for goodwill beyond warranty.
Advisor also told me that while they were replacing screens routinely, they were all still functional and none to her knowledge had failed altogether due to the yellow banding.