i have created a new thread just now about the same issue here
it is a new player issue because i can revert back to plex for android client 7.31 and enable the old player option which totally fixes the buffering but i can not keep using 7.31 because it has the issue with the streams getting killed after 2.5 hours. however, the old player option is missing from all new versions of plex for android clients after 7.31.