Yes, there is a limit on the number of items a menu can have it is defined by the max_input_vars
in your servers php.ini files. Its generally defaults around 1000
which equates to roughly 90 – 100 menu items depending on what else the site is running.
You can try increasing the max_input_vars
to 5000
to see if that helps.
Please note most servers keep the input vars lower to minimise denial of service attacks on the server, so the host may restrict changes to it