Jellyfin struggles to play video files 2/3rds of the time

[TheDreadPirate]

It is extracting subtitles, but very slowly. Between 20-30 seconds. I don't see a lot of Jellyfin related activity in the log during those times, but I don't know what else is running on your NAS to cause it to take this long. Subtitle extract should only take a second or two on a lightly loaded system (either CPU or storage).

You COULD disable on-the-fly subtitle extraction, which is what is causing the playback delay. But doing so will trigger a subtitle burn-in + transcode. Not ideal for the low power CPU in your NAS. Subtitles are extracted for some clients that support directly displaying the embedded subtitle, but don't support doing so directly from the video file.

You could install the "Subtitle Extract" plugin and then run the job for that (Dashboard > Scheduled Tasks > Subtitle extract) and that will pre-extract the subtitles, instead of on the fly, and store them in Jellyfin's appdata dir.