The OP in the first article was saying that when he starts to watch a movie from the middle by fast forward/rewind the subtitles get out of sync with a minor but uncomfortable delay. Once the subtitle gets out of sync the only way to put it back sync is to either start the movie from the beginning or jump back with the back arrow key <- which jumps 10 seconds then after the 1st or 2nd try subtitles are back in sync. The same is not happening on another player like iPad or Chromecast only with Roku
Another issue reported from someone who's using TCL Roku TV:
I’ve experienced this same issue for a long time. It’s possible that it’s always behaved like this for me, I’m not positive. I have a TCL Roku TV. For most videos I watch with subtitles, if I don’t watch it straight through from beginning to end, the subtitles will get out of sync. Either starting in the middle of a video, or rewinding/fast-forwarding a significant amount. I have to “jiggle” it around a bit doing various things, and it will eventually sync back up. I haven’t ironed down a single method that seems to work, but I’ll try just doing the instant replay button a few times like the workaround says to see if that gives me a consistent fix.