Uneven baking — one side of a tray browning faster than the other, or results that vary between the top and bottom rack — usually traces back to one of two places: a convection fan that’s no longer circulating air evenly (worn bearing, obstruction, or motor issue), or a temperature sensor that’s drifted out of calibration and is reporting a slightly wrong number to the control board.
A simple way to help narrow it down before calling: listen for the convection fan running consistently through a bake cycle. If it sounds inconsistent, intermittent, or silent when it should be running, that points toward the fan; if the fan sounds normal but temperatures still seem off compared to what a separate oven thermometer reads, that points toward the sensor.