I have also been experiencing this bug since the latest update was released for Chromecast. Playback will merge between two different users and movies, as long as both of them are using Chromecast. Plex Dashboard will show one of the streams, and a few seconds later the other stream will show instead. After some realtively short troubleshooting, I arrived at the conclusion that what I believe to be the client-id/session-id of the Chromecast doing the playback is not set and/or set to undefined as seen in the logs.
Stream 1:
Oct 01, 2019 22:52:06.572 [2600] DEBUG - Client [undefined] reporting timeline state paused, progress of 513000/1733000ms for guid=, ratingKey=26800 url=, key=/library/metadata/26800, containerKey=, metadataId=26800, source=
Stream 2:
Oct 01, 2019 22:52:10.645 [13016] DEBUG - Client [undefined] reporting timeline state playing, progress of 5999000/8008000ms for guid=, ratingKey=11760 url=, key=/library/metadata/11760, containerKey=, metadataId=11760, source=
Notice the Client [undefined]. I do not know the way plex works behind the scenes, but if they have the same ID, they are probably seen as the same session in Plex’s eyes
I had some logs laying around from Februray of this year, showing that Chromecast used to have unique IDs.
Feb 02, 2019 23:53:08.487 [8752] DEBUG - Client [xjqjbydpgmadqw5nz3xptnnm] reporting timeline state playing, progress of 448000/3704000ms for guid=, ratingKey=24823 url=, key=/library/metadata/24823, containerKey=, metadataId=24823, source=
I hope this will help someone at Plex, please get in touch if you want complete logs as I do not want to post them here.
