A local obstruction can slow water before it reaches the unit. The visible shower waste and the macerator are different points in the route.
What the observation means
Only the strainer or other parts designated for owner care should be cleaned. Removing concealed pipework or the pump cover is a different task.
A useful next step
Follow the shower manufacturer's instructions safely. If drainage remains poor, stop adding water and report whether other connected fixtures have also changed. Do not pour chemical unblocker through the installation or repeatedly fill the tray to test it.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.