Brian,
When the 4-Queens put in their new machine. With the cat red strike chaser. Pete Ryan, Jeff Blitzer, and I watched Shawn(the slot manager) load it. When questioned about the loading. He verified that he decided(and had ordered) to load the tubes. One red in the middle and one at the very top of each tube.
I suspect when you saw the machine the tubes was about half empty. And the red cap on the bottom was one of the ones. That was put in the middle of a full set of tubes orginally. And had worked it's way down near the botttom. And maybe the other red caps, in the ther tubes had already been gotten.
Dan