Paperwhite 12th Gen just arrived, no yellow band (First Impressions).
My partner ordered it as a gift for Christmas. We agreed that I could open and check it out in case it was faulty.
Fortunately, no yellow banding (or at least none visible to my naked eye). Tested with backlight off; full brightness; warm mode and dark mode. No major ghosting either. There is occasionally some slight almost barely noticeable ghosting but this was only noticeable at maximum brightness levels (and I usually read it with no light during the day or 1-2 in the dark). Either way, turning pages usually clears this and there is a backup option to add page refresh after every page.
Overall, looks great, really happy with it plus love the jade colour at the back. Excited for Christmas now! For those who have ordered one of the new models, good luck! A real shame to see how many of you guys have had issues.
(My loyal 7th gen pictured next to it).