Residue concentrated inside folds can indicate that product did not disperse or rinse evenly through that part of the load. It is a different pattern from a stain that has coloured the fibre itself.
Understanding this situation
Check the product's instructions, selected programme and loading arrangement. Tight folds, an overloaded drum or an unsuitable dose can leave some areas less exposed to the washing process. Do not assume every pale mark is detergent: first compare its appearance and whether it can be removed by a garment-safe method.
A useful next step
For the next suitable wash, follow the product and programme limits rather than increasing the dose to improve cleaning. Describe exactly where the residue sits and whether the cycle completed. If marks persist across sensibly loaded, correctly dosed washes, keep photographs or affected items available without running repeated unsafe test cycles.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.