Visibility problem especially with MD and SM breakpoints in preview

Dear blocs pros!

Controlling the visibility of objects with the help of the visibility icons works fine for desktop and mobile breakpoints.
So far so good. But when I am working in MD and SM breakpoints blocs’ preview won’t show objects which I set to visible. Instead it shows the SM objects in the MD breakpoint and the mobile objects in the SM breakpoint. …

Any idea what am I doing wrong?

Help is very much appreciated. Thanks a lot!