Side By Side Shapes - Leaves Gap (Some widths)

On my page I have two shapes side by side that are supposed to appear as though they are one continuous shape, but when resizing the page (and sometime just on initial page load) a roughly 1px wide gap appears between the shapes. (See image below). Again it only happens at certain widths. When you resize the page you can literally watch it flicker on and off. Any suggestions how to fix this?