The starting conditions may differ when a neighbouring cavity is already hot. Follow any restrictions the manufacturer gives for timed or specialised programmes.
What the observation means
A recipe that expects an entirely cold oven is not necessarily being followed if adjacent compartments have been in use. This is particularly relevant to delayed cooking and gentle modes.
A useful next step
Record the neighbouring cavity's use when comparing results. Avoid leaving perishable food waiting in a warm cooker. If an unused cavity becomes unexpectedly hot or controls show abnormal behaviour, seek assessment rather than assuming all cross-warming is normal for every design.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.