Dont know what to tell you. it works for over 1000 people on firefox and over 3k in Chrome. No one but you has reported this as an issue. Its most likely another conflicting addon or an issue with your browser. I'd suggest you try to reinstall Firefox.

P.S.
Yes thats is how dev work functions. You dont drop the ball and work on fixing an issue only ONE PERSON reported over another 4000 plus users. That is non sense and if you want to complain about a FREE ADDON. You are more then welcome to go else where for your needs.