Is the ventilation system contaminated with germs?

Hello dear forum,

my question is mainly about experiences, but also about knowledgeable assessments.

Our central ventilation system (valiant) has been running for 6 months. New building KFW55. Heat exchanger.
The future goes through a 25 meter long earth collector/air well and the exhaust air goes outside.
At the beginning of the supply air there is a "metal mushroom with an additional filter".

In October we noticed that supply air and exhaust air were switched. Water was dripping from the bottom of the system. After changing the hoses, the problem was fixed.

Furthermore, water regularly dripped from the supply air duct - transition to the connection on the wall. A condensate separation is supposed to help here (90 degree KG bend with hose and hole at the bottom, which leads to a lifting system). Not installed yet.
Today I carefully removed the pipe from the wall and about 200 liters of water shot out. Quickly put the pipe back on (surely the same amount is in the earth collector again) and soaked up the water. Dehumidifier turned on again.

So now to the actual question: we have had constant colds for about 6 weeks. When one ends, the next one begins. Does anyone have experience whether a ventilation system under these circumstances actually makes you sick or has anyone had a similar experience? In the earth collector pipe there is a very humid and musty environment. That can’t be healthy.

The ventilation system is off for now.

Thank you very much in advance for all the answers.

There is a study by ETH Zurich (link not possible here) according to which no bacterial or fungal contamination was found in properly executed controlled residential ventilation with preheating through earth collectors. Properly means, in my opinion, at least a fine filter at the intake, suitable pipe material, drainage, and regular cleaning. Your story, however, does not sound very convincing to me.

A photo of the situation would help further.

Was the underground pipe ever dry or is all the rainwater running in there?
Supply air/exhaust air constructed as an insulated pipe or is air condensing on the outside?

Attached is a photo of the system. I can gladly take more photos.

Thank you for the answers.

A photo of the situation would help. Was the earth pipe ever dry or does all the rain run in there? Supply/exhaust air executed as an insulated pipe or does air condense on the outside?

I actually believe that the end pipe has never been properly dry since it started operating. I spoke again with 3 acquaintances and they said everything is dry in their system. Rain could of course be an issue. The supply air inlet is in the west and there is occasionally quite a bit of wind there, which might push the rain under the louvers.