Subtitle is not showing while streaming on website, fullscreen

Hello, I have always encountered an issue where the subtitle in a video is not showing while I’m watching fullscreen. It’s working fine if it’s not fullscreen, but the subtitles never show on fullscreen.

I’ve tried it on Safari, Brave browser, it’s all the same. No matter what’s the websites (YouTube, or other streaming websites) the subtitles is never showing.

If it’s helpful, my Iphone is Iphone 12 and the OS is iOS 16.6.1.

I would greatly appreciate it if anyone know the fix to this problem.

Thank you so much