When the mode knob is set to convection only and tested at 350 degrees the oven works properly and holds temperature within 5 degrees. If mode knob is set for bottom heat with convection the oven is at only 300 degrees although the check temperature function shows the oven at 355. If the mode knob is set to bottom heat without convection the top shelf of the oven goes to 400 degrees while the bottom shelf is at 350. Any mode setting which includes the bottom heat shows these large variations from the desired temperature