I have Plex running on a Apple 4K (5th Gen), streaming from a Synology (running Server version 220.127.116.1173).
My issue is that whenever I try and play a 4K file (same files stream fine to my iPhone, or on the Infuse App on the AppleTV) I get the little spinning wheel for a few minutes and then the App shows the next file screen. If I stop the playback after 2-3min and then restart, the App offers to pickup where I left off, ~15min into the file.
All of this indicates to me that the server 'thinks' it is playing the file at high speed.
Any help or suggestions would be useful!