Plex not showing the full subtitle



Since this is my first post, if something is wrong please tell me.

Now the question. I started to notice it a few weeks ago. I was watching a serie and there were no subtitles when someone talks, but there were subtitles a few seconds back so I thought it was just a bad subtitle file. But last night i noticed it again when i watched an anime. Where with the japanese language it's a lot harder to understand :). I then opened the same file on VLC and my mobile and saw that there were actually subtitles where plex didn't show them.

It doesn't always happen but it's quite annoying. Is this something that's already know or do more people have this problem. Oh and this is on a Samsung Smart TV UE49KU6400.
If someone has some help I would really appreciate it.