I can’t click on the button inside ion-slides, as if the click event on ionic 4 didn’t work
While you wait for better answers, in my experience Swiper.js (on which the Ionic slides component is based) is very event-greedy, and arguably with good reason, as it is responsible for some fairly complex user interaction. So I would not recommend putting anything in a slide that is going to try to need to catch events - move that stuff elsewhere.