Hey, I think those archers are detecting themselves as enemies and shoot. When you hold the left mouse button down and hover over your troops they do that.
Also I think sometimes it doesnt spawn a bought cube.
if is an enemy in a distance of less than 2400 i think , and you move the archer it will shoot to where the mouse is .
i don't have this bug , i spawned over 100 cubes , and no other player has this problem , i will try to to find it and i will resolve it .