[AbRASiON]

Not sure what causes it but it's a known issue. It happens on _every_ 4k HDR video on a non-4k TV. Just try any 4k HDR file and you will see. I'm using WiFi but that's not the issue here.

I thought I'd test but yeah, you're right - it absoloutely is unusable.
I have a 1080p TV, no HDR and every 4k HDR test file I just tried, major issues.

Dunno if it's the processor on the Chromecast (?) or the code in Kodi not stripping HDR as it plays?

Do "normal" 4k movies work?