If you notice one half of your baking tray is browning more quickly than another, the oven is not heating evenly. This can be caused by over-stuffing the oven with baking trays, using dirty or discolored baking pans or by miscalibrating the appliance. Ovens need space for heat to circulate, so you should always allow about 2 inches of space around the baking pans and the oven walls. If a tightly packed oven is not the cause, inspect your baking dishes. Pans should be reflective, but they can become dirty or discolored due to food residue building up over time. You can either give your pans a deep clean or consider replacing them. If you’re still seeing uneven results, contact a repair technician as you may need to recalibrate the appliance.