I have some full screen related problems with:

a) my new Yoga C930

b) Chrome browser

c) multiple streaming sites (Netflix, HBO to name a couple), but not all

None of these problems exist in my other, older Yoga laptop. None of these problems either exist when not in full screen mode. 

Whenever I use Chrome and switch to full screen (either from the video options or by clicking F11) on a streaming service (like Netflix, HBO), the subtitles stay on-screen until the next subtitles are shown. If there is a period of time of no speaking (and thus no subtitles), the last subtitles that were shown stay on-screen until there is speech again, and then the previous subtitles are replaced by the new ones. Thus some subtitles could be on-screen for minutes, so you all surely understand that this is very annoying. The subtitles that are stuck on-screen do disappear each time if i move my cursor, but that's really not a solution.

Another problem with full screen in some (YouTube for example) streaming services is that the graphics showing for example the lenght of the video, the pause button, volume etc. also do not go away at all, they stay on-screen. Neither of these issues occur with other browsers (or the Netflix App), so my first guess was that it's an issue with Chrome. But then again, as I stated above, these problems never came up with my previous laptop, so it can't be only about Chrome, can it?

Did anyone understand my points, and are there some steps I could take to look into this on my own? My C930 is only a few weeks old and to have these issues that affect the user experience and never occurred with my other, 5-year-old Yoga is extremely dissatisfying. I have used Chrome for ages, and switching to a different browser without finding out what's actually wrong would only be dismissing the fact that there is a problem.

Welcome to the Community.

Looking around, the navigation controls sticking onscreen seems to be a frequent problem with Chrome, usually solved by uninstalling the latest Chrome update. Some other solves I found:

Go to Display > Advanced > Display Size and set it to "Default." If it's already set to "default," set it to something else and set it back to "default."

Bring up a YouTube video, go to settings and toggle the PIP mode so that it's off.

I can't find anything on the closed-captioning not properly clearing, but if you try Edge and it doesn't happen there, then it's definitely Chrome. Could be your C930 is on a different version of Chrome than your other computers or something didn't quite install properly during an update. A complete reinstallation of Chrome might fix that or the next update might do it, too.

I'll admit, I've fussed with Chrome quite a bit w/r/t videos, especially longer form things. No matter what I do, it drops frames, pauses to buffer and other annoyances. I'll simply use Edge, instead. Or a dedicated app, like for Netrlix. CBS All Access scrapped their app, forcing everyone to use a browser. Annoying, but I'll put up with it for something such as the "Big Brother" live cams. 

Let us know how you get on.