Problems with Facebook button (Microsoft Edge, I. Expl. &am

Under https://indmarkt. de/I created with the help of the Plugin “Scroll Triggered of box” a Lightbox for the newsletter registration. After 70% scrolling down, the window opens.

According to my tests it functions under chrome and Firefox perfectly.

With Microsoft Edge and Internet Explorer, nevertheless, the button of Facebook “falls down”. (PFA Screenshot…here not possible to add but under the german version to find:
)

Safari kicks the Lightbox half in into the background: (If one again scrolls upwards can recognise it.) though still it covers the Header-Wallpaper, but is overlapped by the contribution side. PFA

Thanks a lot in advance for your help!