The restriction may be local to that fixture or its route, but the observation alone cannot establish the cause. Other normal fixtures provide context, not a diagnosis.
What the observation means
A shared pump problem and a basin waste problem can look similar from the surface. Do not dismantle traps or concealed connections simply to compare them.
A useful next step
Record which fixtures are affected from ordinary use and stop adding water where it backs up. Ask for an assessment of the actual route. Do not assume that replacing the pump will resolve a problem limited to one basin.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.