Agree the normal targets and identify which controls select each compartment. A short visible reference kept outside the appliance can prevent well-intentioned but conflicting adjustments.
What the observation tells you
One person may choose fast freeze while another believes the screen is the fridge temperature. A child lock, if fitted, has a specific purpose and must be used as instructed. It is not a substitute for supervision or proper food monitoring.
A useful next step
Record deliberate changes and explain the reason to other users. If an unexplained problem occurs, preserve the actual settings before changing them again so the repair account remains clear.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.