AEG Competance 5311B-W Condensation

I have looked at the above oven that the customer is complaining about it dripping condensation on the unit below the door when the door is opened.

The venting fan inside the control area is working.
There are no blockages in the vent from the oven or in the vent pipe.
There is air blowing out above the door from the vent.

I placed a roasting tin in the oven with boiling water to test and got a build of codenstation on the oven front panel and oven door inner panel inside the door seal area.

When I open the door of the oven I am engulphed in steam but when I put something glass in front of the vent it doesn’t steam up.

The venting fan draws air from the oven housing as well as the oven cavity, I assume it is only taking the air from the housing. It looks like it uses a venturi affect to drawer the air from the oven cavity so I can’t see why this wouldn’t work.

Any help would be appreciated.

Thanks.