Firefox toolbar buttons invisible/non-functional after update

I had to update Firefox from 47 to 57 due to too many websites having issues with the older version. After the massive headache of having extension & plugins updated without my consent and the hassle of fixing everything I still found it to be complete garbage as Classic Theme Restorer doesn't work in 57, so I installed 56 instead.

And now the back/forward, reload and stop buttons in the toolbar don't work. They are invisible with only empty spaces. I can mouse over to see what they are but they don't work, either. I can remove or add them back in but they don't work. I've tired everything I can find to fix this, Google hasn't been any help. I can't use the browser with these buttons disabled.

I really should have not updated at all, every new Firefox is worse than before. It's either fix this non-functional headache or reinstall 47, live with its compatibility issues, and try desperately to find an older ABP that blocks Youtube ads(this is why I disable automatic updates for stuff!). This is largely why I avoided any upgrade at all, I knew stuff like this would happen.