When hit shift and click somewhere in the webpage or type something, the "Page Inpector" keep poping out (see attached screenshot), this is so annoying that I basically cannot type any capital letters. I have tried the option "Refresh Firefox", the browser seems to be set to default mode, but the issue still exsist. Tried for a new keyboard, the same. I searched the forum, but unfortunately cannot find a proper solution. Hope anyone can help me with this, otherwise I have to consider to change my default browser (which I really don't want to because of such a simple but annoying problem).

Thanks a lot for anyone could provide any suggestions !