This is actually how Plex designed it
From https://support.plex.tv/articles/202605013-play-queue-post-play-screen/
When Post Play Displays And Auto-Advances
…
Auto-advance refers to the countdown timer on the Up Next item, which plays automatically once exhausted. It will be shown whenever there’s an Up Next item, except in the following circumstances:
- If videos have been playing without user intervention for more than two hours, and the video that just completed is > 20 minutes in length. In this case, the Up Next item will still be shown and selected such that a single click plays it.
There’s a feature suggestion requesting an option to actually play videos continuously without such limitations.
