Check your LAN and it’s settings. Plex may be trying to adjust the video bitrate to suit the available bandwidth of your network connection. It will transcode the video to try an achieve that.
if you are using a WiFi connection to the TV, try switching to an Ethernet connection if possible, otherwise, check for WiFi interference and make sure your router is not too close to your TV.
An alternative may be to re-encode your video with a lower video bitrate using Handbrake or similar.
Thank you for those suggestions. I’ll try them out.
