Do not use an open drawer as a diagnostic experiment unless the exact manual explicitly provides a safe owner procedure. Water, detergent and moving dosing components can create unexpected splashes or exposure.
Understanding this situation
Visible flow at one moment would not establish correct operation throughout the programme. Opening the drawer can also change the conditions you are trying to observe and make an ordinary wash unsafe.
A useful next step
Use the final result and any display warning instead. If detergent repeatedly fails to dispense, report the affected compartment, product and programme. Follow only the model's documented cleaning steps after the appliance has safely stopped, rather than reaching into an active drawer opening.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.