watchstate: Plex is not updating its watch progress despite successful watch progress update

Describe the bug Have setup Emby and Plex backends with the primary purpose of syncing watch progress via webhooks. For the purpose of testing, I am doing manual sync. If watching a movie in Plex, then it will sync progress to Emby just fine - this works consistently and reliably. It does not work the other way around, Plex will not update its watch progress after viewing a movie in Emby.

After watching a movie in Emby and stopping playback, I can see the update is queued:

2024-04-26T10:07:23.596790203Z [2024-04-26T20:07:23.596460+10:00] http.INFO: Queued [emby] movie [I See You (2019)]. [] []
2024-04-26T10:07:23.597496693Z INF | ts=1714126043.597315 logger=http.log.access msg=handled request request={"remote_ip":"192.168.0.196","remote_port":"38778","client_ip":"192.168.0.196","proto":"HTTP/1.1","method":"POST","host":"192.168.0.179:8076","uri":"/?apikey=xxxxxxxxxxxxxxxxxxxxxxxxxxx","headers":{"User-Agent":["Emby Server/4.8.5.0"],"Accept-Encoding":["deflate"],"Traceparent":["00-86b684d41fe9d36abc5a30ed4257b155-456df76a2069aaf2-00"],"Content-Type":["multipart/form-data; boundary=\"42dcdfb1-16f7-4145-87ac-d976ef28d205\""],"Content-Length":["2859"]}} bytes_read=2859 user_id= duration=0.00872294 size=0 status=200 resp_headers={"Server":["Caddy"],"Content-Type":["application/json"],"X-Application-Version":["20240423-03e7c1e"],"X-Request-Id":["49d6a9b9-a096-4cff-844d-e7c2163c393d"]} 

I then use the following command to do a manual progress sync

docker exec -it watchstate console state:progress -vvv --trace --context

Viewing the output below, I can see that it is successful in pushing the progress state to Plex, but in the Plex app I see no change to the watch progress.

[2024-04-26T20:07:36+10:00] INFO: Emby.Progress: Ignoring [I See You (2019)] for [Emby: emby]. Event generator. { (item: [ (id: 358), (type: movie) ]) }
[2024-04-26T20:07:36+10:00] NOTICE: SYSTEM: Sending [1] progress update requests. { (time: [ (start: "2024-04-26T20:07:36+10:00") ]) }
[2024-04-26T20:07:37+10:00] NOTICE: SYSTEM: Updated [plextv] [I See You (2019)] watch progress. { (item: [ (id: 358), (type: movie) ]), (remote: [ (id: 36305), (url: https://192-168-0-xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx.plex.direct:32400/:/timeline/?ratingKey=36305&key=%2Flibrary%2Fmetadata%2F36305&identifier=com.plexapp.plugins.library&state=stopped&time=3245869&duration=5862040&X-Plex-Client-Identifier=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx) ]), (status_code: 200) }
[2024-04-26T20:07:37+10:00] NOTICE: SYSTEM: Sent [1] watch progress requests. { (time: [ (start: "2024-04-26T20:07:36+10:00"), (end: "2024-04-26T20:07:37+10:00"), (duration: 1) ]) }
[2024-04-26T20:07:37+10:00] NOTICE: Using WatchState Version - '20240423-03e7c1e'.

Then right after this, without any further action, Plex will queue an update itself - unsure of this behaviour and why it is happening.

2024-04-26T10:07:37.060202138Z [2024-04-26T20:07:37.059966+10:00] http.INFO: Queued [plextv] movie [I See You (2019)]. [] []
2024-04-26T10:07:37.062252438Z INF | ts=1714126057.0621612 logger=http.log.access msg=handled request request={"remote_ip":"192.168.0.193","remote_port":"40628","client_ip":"192.168.0.193","proto":"HTTP/1.1","method":"POST","host":"192.168.0.179:8076","uri":"/?apikey=xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx","headers":{"User-Agent":["PlexMediaServer/1.40.2.8395-c67dce28e"],"Accept":["*/*"],"Accept-Encoding":["gzip"],"Content-Length":["7279"],"Content-Type":["multipart/form-data; boundary=------------------------9zvwhyV6v12loEgcsyjoaQ"]}} bytes_read=7279 user_id= duration=0.034613072 size=0 status=200 resp_headers={"Server":["Caddy"],"X-Application-Version":["20240423-03e7c1e"],"Content-Type":["application/json"],"X-Request-Id":["2542a78d-7d8a-4962-b352-b9440c246584"]} 

Additional context I am using Plex Server Version 1.40.2.8395 in a docker container and Emby Version 4.8.5.0 also in a docker container.