Slider elements are never visible

After installing the enfold theme on my latest site with Enfold 2017 demo on all pages the slider elements are never visible: easy slider, fullscreen slider, accordion slider. The only similar function available is WP Layer Slider. The feature is also not available for rotating blog posts, photo gallery and testimonials. The elements on page are present, but not visible or with opacity 0. The theme was set as usual, without changing the css, but inserting these styles on the additional css solves the problem for single elemente. Is it a bug with enfold’s css? Is it possible to fix it?