Subtitle Problems: Language and Font Weight

I have a couple of problems regarding subtitles. I selected Turkish as the subtitle language in settings page. But every time I open a video, it plays with English subtitles, even when Turkish subtitles are available. It’s like default like is English when it’s not. And when I switch to the Turkish subtitle on fly, the font weight turns to bold. I have to go back and play the video again for the font weight to be normal again.

These issues occur on both iOS and tvOS.