Button trouble: consecutive clicks cause different behaviors

Hi there

I’m trying to build a site where certain elements appear and disappear when clicking a button. It works for the most part except two weird problems that i can’t explain:

  1. the menu items in the main part work correctly right after the page has loaded. however, once they have been clicked on the first time, every interaction requires two clicks for it to work. why?

  2. the top nav has buttons that makes an element slide out from the top. the smooth sliding interaction never works on the first click, where the element just pops out instantly. after the first click, they move correctly.

I have no idea what causes that behavior.

Any help is greatly appreciated!

(the site is in no way mobile-ready. i first need to fix this problem.)

Here is my public share link: LINK