I have found something that must be some kind of bug. I have isolated it in this example.
You can aim the "cannon" with the mouse and press the left mouse button to shoot the "bullets" toward the blue object. It is set to fine collision but as you will see it behaves very strange. The bullets stop at the wrong place. Also this only happens if I have the event to scale the blue thing to 0.5 at the start of frame. If you erase that event it will work as expected. Any ideas why this is happening? Any way around it?