The volume should not be able to move on its own, but when the popup.htm is opened, the slider is highlighted. So if you're in windows for example and have a controller plugged in, it interacts with the slider so controller drift can be an issue in that case. But otherwise I asusme your issue is not the extension itself but the videos you're watchin/diferent scenes being diferent volume. In which case you'd want a normalizer. But I don't think there's a way to do it in chromium rather you should use third party application for example I have a python one in progress which is published in my github for windows....