Greasy Fork

Sometimes the video doesn't load and if it does the loading icon doesn't disappear. Can be fixed by manually pausing the video every time.

There is a mechanism in Youtube to check whether the video is smoothly playing or not.

As this script highly reduces the execution frequency of the timers, the mechanism would falsely believe there is a loss of connection.

I would recommend you to try https://greasyfork.org/scripts/431573-youtube-cpu-tamer-by-animationframe which is to strive for a balance between performance and energy impact.