Tray shape, spacing and position can create a local result. First distinguish a repeated oven-side pattern from differences caused by the tray or the portions themselves.
What the observation means
A tray pushed close to a wall or blocking airflow can expose its contents unevenly. Dark coatings and raised edges also influence how heat reaches individual pieces. If the effect belongs to the same tray edge after ordinary use, that is different evidence from food always darkening at one side of the cavity. Do not perform repeated baking tests merely to investigate.
A useful next step
Record the tray material, shelf and selected mode from the affected batch. Follow the recipe's spacing guidance and the oven's permitted loading layout next time it is safe to use. Persistent directional scorching under suitable conditions merits an appliance assessment.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.