Convection ovens operate on the mistaken theory that you can put a cheap @$$ fan in the corner of an oven and create even circulation to balance out the normal hot/cold spots that cause uneven cooking.
BULL$&!T.
What the stupid little fan does is to concentrate the hot spots and cold spots and increase uneven cooking.
In a commercial bakery, it can lead to hilarity, when cooking some paper thin cookies like Pecan Thins that are mostly egg white.
What happens is that they lift off of the Silpat baking mat and fly out the back top of the oven where the vent is.
In every kitchen I ever worked in, if there was a switch to turn the fan off, I turned it off, taped over it with HAZARD tape and put a note on it to not turn it on.
Amazing what you can get away with if you have some official tape and a notice.
/johnny