Integrated Slider shows "white" featured Page Photos

Dear Support, I am working on the web site of a theatre company and have problems with the integrated slider in Fabulous Fluid Free. When I open up the website: wp.theatercourage.de the first silder photo is loaded correctly, so far so good. The second photo sometimes works fine too but then mostly only a white browser background is appearing for the other three pages. I already tried all available different effects & settings in the customizer but nothing helped. Best regards Martin