Hi, i don't know if you can fix it since you know a bit about the history structure on firefox..
the addon noun biuttons stopped functioning because its xul based since firefox 29
i'm actually on ff44.0.2, the only one supporting all my addons, will not upgrade to loose all those contributtors addons functionalities.
the actual issue: noun buttons used to show ONLY the back history browsed left clicking on the left button, & ONLY
the forward history left clicking the right forward button..
it would be nice if you could create an addon to revert to the previous unconfusing display of history dropdownmenu for back/forward buttons after australis arrived..