We have a problem on a website. Recently updated Wordpress (not 4.5) and Appearance > Menus is broken now.
I have tried diabling all plugins, and the problem was there. So I tried switching a theme on one of the multisites, and the problem was fixed.
So I know that it's something in this custom theme, but we can't figure out what.
Our theory is some kind of enque issue / conflict.
If you can elp solve this, it would be very much appreciated.
Many thanks in advance