I am trying to sideload the subtitle tracks, my content has Korean/Vietnamese subtitles (these are in .SRT files). But the player doesnt render it properly, it shows up like this  .!
This issue has been driving me crazy? It was working fine before and now it just displaying square symbol.
Screenshot down below
These same srt files played before or are you saying other korean files played? If these played once fine then that is odd, but not ruling out that you just downloaded improper sub file. Have you viewed the srt content to see if it is right?
You don't state which roku you use. I just visited a family member and two of two movies had srt/subtitle misbehavior. His was a 2XS, and subs would stop and restart.
That's a TCL 4K Roku TV.
I have no ideas but hoped that keeping your thread active someone else may suggest something. Maybe I'll download a korean sub file for one of my movies and see what I get.