https://www.techradar.com/news/itunes-bug-causing-many-users-4k-titles-to-be-downgraded-to-hd

Back in 2017, Apple TV 4K users cheered when selected films in their iTunes libraries started receiving Ultra HD upgrades at no extra cost.

Now, it appears the opposite is happening (albeit unintentionally), with both purchased and unpurchased 4K movies being downgraded to HD thanks to an alleged bug, as reported by 9to5Mac.