Exactly same thing here. Streaming Plex to Chromecast on OS X El Capitan (v 10.11.16). Trying to downgrade to an older version of Plex, hoping this bug was introduced recently. There seem to be no more older versions archive, so I found this: https://www.reddit.com/r/PleX/comments/4rf40b/where_can_i_download_old_versions_of_plex_media/
