Well, after a disappointment in a large chain store (no names no pack drill, but their logo consists of a red circle surrounding a red dot, all on a white background) which had a sign on the shelf saying "Sony 4K blu-ray player $79.99" only to find out that price was for a (conveniently out of stock) 4K upscaling player and that the the price at the till for the 4K player was actually $149.99, we went to another big chain and bought a second X800 for the living room.
Just watched Alient Covenant, superb picture on this TV which, unlike the one upstairs in the media room, is HDR, but no surround sound. Burger (cough). About to watch Atomic Blonde again. So far no freezes. Maybe the firmware updates fixed the problem, who knows?