Here’s my configuration :
Shield TV2019 version 8.1.1
Marantz HDMI AVR with 2.0 cable
Sound configured to automatic or manual and dolby disabled
Video set to 2160p HDR10 60hz
Plex client tested - all of the version starting 7.26 to 7.28
Plex server latests version
Use case 1 => PLEX CRASH
Shield TV Video Set to 2160p HDR10 60Hz
Play player set to HDMI Passthrough / old player / autorefresh
I can play any movies 1080p, plex switch refresh rate perfectly
Starting 2160p/24 Hz movies (HDR or NOT), movie start, and plex client crash
Use case 2 => WORKING
Shield TV Video Set to 2160p HDR10 24Hz
Play player set to HDMI Passthrough / old player / autorefresh
I can play any movies 1080p, plex switch refresh rate perfectly
Starting 2160p movies (HDR or NOT), movie start, and works perfects because it don’t need to switch to 2160p 24Hz
So to resume issue is from switching to 60hz/50hz to 24Hz WHEN playing 2160p movies
I tried with Emby => no issue
I tried with Kody => no issue
A suggestion => why not adding a pause (like kodi) between refresh rate switch and player start
Hope this help solving the issue