Semantic ui sticky menu goes adds classes "bound bottom" when scrolling

I have a semantic UI sticky menu. I've used it exactly the same way (same skeleton) on other websites and usually when the scrolling down on the page the menu gets the classes "fixed top" which... keeps it fixed to the top of the page. This time though, after scrolling past my banner, it gets the classes "bound bottom" which keeps it at the bottom of its parent element (the body). I don't understand why those classes are applied or how. I've tried adding "fixed top" to my menu but the classes get removed and "bound bottom" reappears as soon as I get past scrolling a certain point.