Parallax under Chrome and Safari

Hello.

On our Sydney Pro Startpage we use the Background Parallax Picture in four sections.
Under Firefox theres no Parallax but every section has the background image.

Under Chrome (an also Safari on Mac) the first section “Produktions-Timeline” first shows the normal background and the background-image goes over it while scrolling.
The three other sections “Wer wir sind”, “Unsere Partner” and “Kontakt” didn’t show any background-image.

You can see the effect in this GIF.
Also on the website itself: https://www.lichtfilmkonzepte.de/

Installed is the latest Theme-Version 2.0.28 (from today).

Thanks for your support,
Jörg