After using this addon for some years, all of a sudden youtube.com redirected to a post on a page from a channel I have visited in the past. The page was hanging on this post and refreshing all the time. Couldn't solve it by deleting cache, cookies temp etc. Opened youtube.com in MS Edge and no problem occured. Restarted FF in save mode, without addons enabled! No problem with youtube. So I disabled all addons and one by one enabled them again. Found out that 'Youtube High Definition' was the problem of the redirecting of youtube.com homepage. I removed the addon from FF.