Was your basket full of fuel, and did you only light it in the center? I find starting this way gives me a more uniform airflow, it just takes a little longer to come up to a temp like 400F vs. lighting in several spots. I find when I light in several spots, some take, some don't. That can give you different results around the perimeter.
That said, anything near the edges at 400F with a heat deflector in is going to cook in a hurry vs the stuff that is centered. Doesn't matter what you do.