Swiper previous/next buttons don't work properly with ionic framework

[tema-303]

Hello!
Could you please help me?
I am trying to use swiper in ionic framework. I followed this instruction:
https://ionicframework.com/docs/angular/slides

The problem is that the swiper is displayed on the page, but the previous / next buttons do not work. At the same time, it is perfectly scrolled by dragging. But when I added a simple button and moved the register() method to click on this button, then when I press it, the swiper buttons start working as they should.
register() in ngOnInit and in ngAfterContentInit don't make the buttons work either.
What could be the problem?

[tema-303]

When creating the project, I set the blank template. Thus, I display a page with a swiper inside the ion-router-outlet. At the same time, the initialization function in swiper-element-bundle.js is called not once, but several times. If I display the swiper directly in app.component.html, bypassing the ion-router-outlet , the problem goes away and the initialization is called once. How can I get around this?