I have – or rather had – a main menu with several sub- and sub sub menus (more than 100 entries in total).
Now I needed to update a menu item and after saving the menu was no longer displayed.
A look in the WP dashboard has shown that the menu has been set to inactive and worse: it has been cut off after the first 90 menu entries.
The rest is gone.
I’ve tried to create a new menu from scratch. Adding menu items and saving works fine … until I reach the 90 entries count.
Same thing happens again: On ‘save’ the menu gets disabled and additional entries are not saved.
The problem did not exist when I first created the menu a few month ago.