I have been noticing what appears to be a bug with the hide empty elements option.
If I am on a single page and I click on the option in the left sidebar to hide empty elements when in preview mode, and I click on preview mode, the empty elements are indeed hidden.
However, if I happen to click on a link to a different page while in preview mode, any empty elements on that new page then show up (despite hide empty elements being selected for every page).
I can’t tell if there is something I’m not doing, or if this is indeed a bug in the functionality.
from what I can see on screencast it is not an error or bug.
If you put empty element on the site body and do not style it it has no width and no height, so when browser reading the site code it do not display that empty element. Webflow Designer mode just let you see that element and shows like semi-transparent box.