some european 500s were fitted with a fan on the rear of the oven cavity.If yours is a fan assist,check as to whether it is running when the oven is operating.If it isn't the fan has failed and needs replacing.If yous is the 500s with combined oven and grill then the ovens thermostat has most likely faild.That's the dial to regulate oven temp,not the selector switch.As for the door seal iam not sure maybe someone else can elaborate.
paul
January 2012