1Password, uBlock Origin, and uBlock Matrix add-on icons are continually disappearing from my toolbar. All of the add-ons are current and signed, so FF should be happy. If I use the 'customize' menu to alter my toolbar icons, I can place all of these add-on icons where I want them - as expected. After some time (a day or so) of browsing I'll notice that one or more of the named icons are missing. The quickest way to get them back is to once again 'customize', but click 'restore defaults' and then 'undo'. Magically, the missing toolbar icons return. Why does this happen? They clearly _can_ be displayed because they are when I mess with them and set it all up. So why would they disappear over time? Confused.