The cooking duration is insufficient.
Extend the cooking duration.
The food is not sufficiently baked after following the times given in the baking chart.
Extend the cooking duration.
Remove any accessories that are not being used from the oven. Also remove the grease filter from the oven, as this obstructs the flow of air. Only insert the grease filter when grilling or roasting.
Use dark, thin tins if possible.
Check the ingredients and adjust the cooking duration.