Strange aircon smell query

[quins]

Hi. I have had my aircon cleaned using the various sanitizers available. Every air vent now seems to smell fine except the downward blower in the passenger footwell ONLY!!! I have replaced the pollen filter. This seems a bit weird to me???? Does anyone know why this one should smell only and if so how and where to clean it as it really makes the car smell. Many thanks.

Tim