This happens on complex streaming sites that split audio and video into separate streams. Try selecting a different resolution option from the extension menu, as alternative streams often align better.
This guide provides a detailed overview of what this tool offers, its potential risks, and what you need to know before deciding whether to install it.
: Because it merges files in your browser tab, downloading very large videos (over 2GB) can sometimes cause the browser tab to crash if you have low RAM. Legal Note