Usually I manage to find a solution but today, it seems I can’t resolve this mystery
I have a very simple mosaic page with 50% Float Left Containers.
All images have the same sizes in order to ensure a proper display.
99% of the time it displays the page the way it is intented.
But for some reason, if I redimension the page to test the layout, some of the Floating Containers seems to overlap and create a white space… you can actually see there’s a glitch when you drag your browser to redimension… You see one of them who wants to move
I’m not able to recreate your issue when I use the share link (designer) are you able to reproduce the issue with the designer or only on the published site?
I have a very similar design as your site - mine does not appear to have the issue. The only difference is that I set my section to be 100% width that holds the partial % elements (in your case the section that holds your 50% elements) try setting it to 100% width and see if that corrects the issue.