Any overflow value other than visible and no height is the enemy of child elements with position: sticky;. It's like that element is ready to stick when the parent scrolls, but it never does because the height is unconstrained. Adding a fixed height can solve the issue, but that's not always desirable.
Dannie Vinther digs into a way of dealing with that. The end result is avoiding that situation all together by removing the element that wants to be sticky from the element that needs an overflow. But as soon as you do that, the elements no longer scroll together since they aren't siblings. The use case here is a table with sticky headers on vertical scrolling and allowing for horizontal scrolling as well. Dannie uses a script to sync the scroll positions.