Firefox and Chrome same behavior. Since latest server update, web player won’t complete movie. It is stalling or buffering right at the end of a movie (2-3mins left) and will not continue to next movie in queue. It appears if you fast forward to end, then it will move on to next movie.

Since latest server update, web player won't complete movie

DeanMarkTaylor January 29, 2022, 7:26pm 10

For me the issue described by OP seemed to happen around the same time as this:

Topic		Replies	Views
Plex stops buffering Desktops & Laptops server-windows	8	222	May 10, 2022
Plex Server began buffering in web browser Desktop Players plex-web	5	576	July 9, 2019
Plex video stops consistently on browser, not on app Desktop Players server-linux , plex-web	11	1437	April 3, 2022
Web Player out of buffer Plex Players server-linux , plex-web	26	579	July 26, 2022
Plex Web stops buffering after 2 mins causing playback to stop Desktop Players plex-web	203	8149	July 8, 2022