YS 640 Hotter on left than right

I have a question after reading the manual and seeing that the smokers temps can be adjusted by moving the damper. I moved mine from one side to the other and I am always getting hotter temps on the right side of the smoker than the left. I have the diffuser in and it does not seem to matter where I pull it to.
Why would this happen and thought this was the design of the smoker. By the way the probes are on the top grate if that matters.
Why would this happen and thought this was the design of the smoker. By the way the probes are on the top grate if that matters.