Server Version#: 1.21.3.4021
Player Version#: 8.12.4.22902 (Android), 7.12 (iOS)
Ok first, my Plex Server is on the same network as my devices (iPad and Mi 10 Pro).
Second, syncing takes awfully slow (even stuck on Pending with no Upload activity from my Windows Server running Plex Server).
Now, i can’t sync a media file at all. And yes, i am a Plex Pass subscriber. I’ve done this before with success (and still taking awfully slow!) but just can’t right now. Everytime i press the Sync button and confirm my desired quality (Highest/Original), i lose connection to the Server and to my surprise, when i check the host PC, the Plex Server icon on the Notification Tray is gone (crashes).
According to VLC, this is the Codec information of the media file i’m trying to sync:

I tried it both on my Android Phone (Xiaomi Mi 10 Pro 5G) and my Tablet (Apple iPad Pro 10.5" 1st Gen) - both resulted in a server crash.