In your connection diagram it looks like the red power bus on the top is positive relative to the blue, but opposite on the bottom busses.

 

Double check all the wiring as compared to the schematic. Sounds like a wiring error.

I was hoping that would be the issue but I have rewired the circuit three times according to this schematic and have gotten the same result. Do you have any suggestions of what else to try?

 

In your connection diagram it looks like the red power bus on the top is positive relative to the blue, but opposite on the bottom busses.

You're right! That would be terrible. I made that mistake while drawing the diagram, however, on my circuit it is correct.