Overfilling a conditioner compartment can interfere with the intended dosing behaviour. The maximum mark matters, even if the compartment appears to have enough physical space for more liquid.
Understanding this situation
A drawer section may use a siphon arrangement rather than a simple open cup. Filling beyond the intended level can allow liquid to move earlier than expected, which differs from conditioner remaining behind after a programme. Thick products and a displaced removable insert can produce other patterns, so describe which behaviour you actually see.
A useful next step
Measure below the marked limit and check only the removable drawer parts identified for owner cleaning in the manual. Do not poke tools into the washer or add water blindly to a loaded compartment. If the correct amount continues to disappear at an unexplained stage, record the programme and drawer arrangement for a model-specific enquiry.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.