The unit or part of its discharge route may lie outside the room where the symptom appears. The appropriate access and responsible person need to be available.
What the observation means
A repair business should not be expected to enter locked communal spaces without arrangement. The owner should not open restricted panels to prepare.
A useful next step
Explain what is private and what is shared, and provide existing installation information. Stop affected use where necessary. Keep permissions and building access separate from the technical diagnosis so the visit can address the actual system without improvised entry or pipe alterations.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.