On what exact player app/version are you experiencing this (given the Plex Media Player desktop/HTPC app has long been discontinued and replaced by other apps). Or do you experience the same behavior on different Plex clients?
If i screen share from my samsung phone (synology NAS) to Samsung smart monitor its like my settings aren’t there and annoying tv theme tune playing in background and i have to choose play version to get it working.
On my standard 1080p TV in bedroom my 4K TV series don’t play the loading circle animation spins foreve. If i select play version it works!
It doesn’t sound like you are screen sharing. Sounds like you are using the Plex remote companion feature where you can use the Plex app on one device to control the app on another. So your phone is controlling the Samsung smart monitor’s Plex app and you have theme music turned on in the settings.