Seems that GraphicRaycaster raycast behind objects and override UI events.
I don’t understand the question, could you describe it in a bit more detail.
the cube behind the Canvas is treated as a blocking object
How close are the canvas and the cube? if they are intersecting there might be an issue with precision here.
I’ve tested several distances, seems that if Canvas is 1< unit near the cube, it’s treated as a blocking object.