Masonry grids may overlap if the height of a grid item is unknown. This can happen when css is applied after the grid has been laid out or when the grid resizes and the width changes. These settings are not available in the widget and must be applied in the shortcode.
There are some circumstances when layoutonresize is true automatically. When the grid contains items that have no image or when excerpts are displayed. In other circumstances, you should enable this value yourself.
This is a css value that defaults to 500 (ms).