Only one side burns in my Mini WSM

I notice my Mini WSM likes to burn the lump charcoal on the left side every single time. I stoke the coals moving red ones over to the right side.. I check back later and again the left side is glowing red and the right side is out. The Mini WSM has equal airflow all the way around the bottom.

I am using the Smokey Joe Silver, with a 16 guage expanded metal grate over the stock charcoal grate to help catch smaller pieces of lump. I have an oversized tuna can with 16 x 3/8" holes drilled around the top of it to keep the coals from clogging the vents.

I've rotated the exhaust vent before and it didn't seem to make the fire move from one side to the other. I'd think ideally the exhaust would be in the center of the top like in the big green egg or some UDS i've seen.