Question Canvas with "Screen Space - Overlay" not rendering on top of everything

I'm having an issue where sometimes my menu is not rendering properly due to objects behind the menu. The Canvas is set to Screen Space - Overlay, which I thought meant it would appear on top of everything. The issue can be seen in the below screen shot, where the circles are blocking the UI text. The circles are gameobjects with meshes that are placed in the world.



Any thoughts and suggestions are appreciated!