The selected mode and shelf arrangement may not support identical results on both levels. Conventional and multi-level fan programmes have different loading guidance.
What the observation means
Even a multi-level programme needs the specified shelf positions and suitable spacing around the tins. Two large tins can restrict circulation more than the smaller examples in a cooking chart. Different tin colours, depths or quantities also prevent a fair comparison. A second shelf does not automatically mean the oven can duplicate a single-shelf recipe without adjustment.
A useful next step
Check the model's multi-level cooking table before the next suitable bake. Keep the two tin types, levels and quantities in your notes. If equal loads on approved positions repeatedly behave very differently, report which level changes and whether the selected function is genuinely intended for multi-shelf cooking.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.