Further inflow can overflow the tray if the system is not clearing. A delayed start or familiar sound does not guarantee it will recover in time.
What the observation means
The shower, local waste and pump are separate parts of the route. Waiting with water running can hide the original pattern and increase damage.
A useful next step
Turn off the water safely and keep the affected fixtures unused. Record whether the motor started and what the level did. Do not open the pump or use a chemical treatment while the tray remains full.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.