I am unable to save edited header menus. Under Appearance > Header it allows me to add/remove menus however when I try to add items into the menu the Save and Publish button stops working. Looks like it tries to load then just stops. If you try to exit it prompts giving a warning that leaving will undo changes and then changes fail to save.
I have disabled all plugins – still no change
I have removed all plugins – no change
I have swapped themes – no change
Any ideas or a way to manually edit the menu items would be great.