Should there be a gap in my oven door seal ?

Hi,

i have a diplomat softline adp0500 gas cooker and we are experiencing massive cooking times and cant seem to work out why ??

we checked the door seal and noticed that at the top in the centre there is no seal over a length of approx 6 inches but there is a small slim metal plate so we assumed there needs to be no seal there but surely this is allowing heat to escape which we can feel coming out of the top of the door when the door is closed.

Its taking 3 x longer to cook food when compared to food cooking times so can someone please tell us if there should be a seal all the way around the door ?

also should we be able to feel the heat coming out at the top of the closed door ?

Please help by answering as we are struggling to cook meals and have children that are waiting over an hour for meals.

Thanks