I found the answer to my question here: https://www.ads-software.com/support/topic/wordpress-3-menu-feature-500-internal-error?replies=7
Just like the other person said, for some reason it had to do with having too many menu items – not that it should matter really – but I removed a bunch of the menu tabs and now it works perfectly. Guess I’ll just have to limit the number of drop-downs.
