On using F11 to go to fullscreen or back (is that reflow?), the page elements realign themselves properly to close up the gap. Also, reloading the page with the stories offscreen seems to make it more likely for the problem to occur.
Those attributes need to be correct and in place in the html.
Without those natural width and height attributes the browser won’t be able to calculate how big the image is even if you resize or set the size in css. It will only know once it has loaded and cached the image which is why a refresh or a reflow is required.
Also absolutely placing all your content is bad if you are doing this yourself. Its ok for something like masonry to do it because it is reorganising the content but inevitably it causes issues.