YouTube page keeps refreshing when the extensions Appearance setting does not match YouTube's Appearance setting.
Workaround
If the video page keeps refreshing you can workaround the problem by following these steps:
Go to the YouTube homepage
Change the appearance to Dark (or Light) so that it matches the Appearance (theme) setting in the extension
After that you can go to a video page and change the extensions Appearance (theme) setting to Default which will allow you to set the YouTube setting's appearance to Dark or Light according to your preference
This is caused by a code change in YouTube since today that refreshes the whole page when you change the appearance from Light to Dark (which does the extension automatically for you)
YouTube page keeps refreshing when the extensions Appearance setting does not match YouTube's Appearance setting.
Workaround If the video page keeps refreshing you can workaround the problem by following these steps:
This is caused by a code change in YouTube since today that refreshes the whole page when you change the appearance from Light to Dark (which does the extension automatically for you)