The browser tools (not web developer tools) aren't opening. I could make a guess that it's because I exited my firefox session before closing the browser tools. I will say that now "Disable popup auto-hide" is always on. I wanted to customize the browser with userchrome.css and was doing a good job until I couldn't open the browser tools.

edit: I found out that when trying to open the browser tools 1 or sometimes 3 new processes run, but only for a few seconds.