4K titles slow, prohibitively slow w/ subtitles on 2026 Onn 4K Pro
I am an amateur Jellyfin user getting by on tutorials and YouTube videos. I use MakeMKV to save MKVs with PGSUB subtitles on a Synology DS220+, streamed to a local 2026 Onn 4K Pro over 500Mbps (albeit wirelessly).
4K movies may take a few (2-5?) minutes to load, but when I turn subtitles on, it takes so long that it reverts to the Onn home screen due to inactivity.
I have HW transcoding turned on but it's rarely needed, and the only thing I've tried is turning off the "Allow subtitle extraction on the fly" setting in the server Transcoding settings. That didn't seem to help.
Are there any low-hanging fruit options for me to try first? I have seen a couple things to try, but I wasn't sure if I should try them in a particular order: (1) Extract Subtitles scheduled task, (2) Save subtitles into media folders (I'm not sure if this is even possible for me having it all in one mkv), (3) Bazaar. What should I try first? Anything else I'm missing?
Or is this the type of problem only solved by an NVIDIA Shield Pro? Or a direct ethernet connection to my modem? Or upgrading my internet bandwidth? Or is it the DS220+?