If you have a custom menu on your WordPress site, and you’ve found that after adding so many items, saving the menu will remove the last few items from the list. This will generally happen if you have many sub menu items.
The main culprit is the “max_input_vars” PHP setting. By default this is set to 1000, which limits your menu to ~75 items. I’ve seen some hosts set this to 500, which gives you ~35 items before things start getting chopped off.
If you have the ability to edit your site’s php.ini file just add or modify the following line:
max_input_vars = 5000