Surfaces pressed together can be sheltered from the wash. A nested pair may therefore leave food between the bowls while exposed areas look clean.
Understanding this situation
The appliance needs water to reach and leave the items in the arrangement described by its loading guide. Simply fitting more pieces into the rack does not establish that they can be washed effectively.
A useful next step
Separate the bowls and use the intended supports without forcing them. Check spray-arm clearance before starting. If poor results persist with a suitable arrangement, record the affected positions and programme rather than assuming one dirty nested surface proves pump failure.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.