Not preheated enough

Use preheat time, extend preheat time

Suction panel not fitted correctly

Check the installation of the suction panel as to whether all attachment points are seated correctly and closed

Hygienic plug-in gasket worn

Replace the hygienic plug-in gasket

Uneven loading

Distribute the load evenly in the cooking chamber, i.e. starting from the centre, distribute it evenly over the entire cooking chamber and ensure adequate air circulation by providing enough air space between the food containers.