Ventilation in the dressing room on the attic floor was forgotten

Hello everyone,
we are finally living in our KFW40 house, which really went through ups and downs.
Basically, there are only "minor issues" left, although almost all were unnecessary and known.
DEKRA has approved the house and we are still living in a 4/5 construction site.

Anyway, I happened to notice recently that the ventilation is missing in the dressing room in the attic.
We usually have it in the ceiling, rather at the edge of the room, and in ALL 9 rooms.
Even in the basement they are there, except for one very small storage room on the upper floor.

I only noticed this because it was very warm and musty in the still unfurnished dressing room.
Today the construction manager and the "climate technician" (?) were already here and looked at it.
Of course, now the blame is first being shifted aside and "it was forgotten" is not even mentioned.
It was built exactly as it was in the plan. This plan is now being requested to see if it is included.

If it is included, the matter is clear, if nothing is included, the matter should also be clear, right?
I think this will definitely end in a dispute, but what does it really look like professionally/legally?
Do I have to accept that the ventilation is missing in such an important room where all our textiles are stored?
And how can this be solved "uncomplicated"? Suspended ceiling? Or breakthrough to the WC next door?

Thanks for your opinions/tips.

The decisive factor is the mentioned plan, it will show that, along with the contract or the agreement which states that that plan is to be carried out.

Only who decides whether a ventilation goes in there or not?

The catch: In the 2nd construction phase there is a house that has almost the same floor plan in the attic.
Bedroom, small WC, dressing room. Slightly differently shaped, but identical.
There is a ceiling ventilation in every room there.

In my opinion, it is absolutely not such an important room as you write. After all, only textiles are stored there. No one really "lives" there. You are only there briefly, your clothes come into the closet bone dry, there is no moisture inside. You don't ventilate a wardrobe either, do you?

It was built as it was in the plan. This plan is now being requested to see if anything is in it.

You should have the plan: just go through the building application. Or the execution planning.

I think this will definitely end in a quarrel, but what does it really look like technically/legally?

Why? Who should argue? Don’t you make mistakes? It’s annoying, but no reason to lose your level of civility.

Do I have to accept that the ventilation in such an important room where all our textiles are stored, is missing?

No, it will come down to a compensation payment.

And how can this be solved "uncomplicated"?

Manual ventilation? Or install a decentralized ventilation system in the room.

I don't want to go into detail about how the house construction proceeded and still is. Plans were often changed without informing us and in the plan I approved, there are generally no ventilation systems indicated. The technician once showed me one on the phone, something I had never seen before.

BTW INFO: We built through a developer! Who also provided the craftsmen.

Sure, mistakes happen sometimes, but our small list of errors is getting longer day by day. These aren't even extreme issues. Basically "just" basics that every apprentice should know. Anyway, that doesn't matter here, the fact is, the ventilation was obviously forgotten there.

Even if you try to sugarcoat the issue with clothing now, how does it look regarding KFW compliance? I think for KFW40 it is quite important that every room in the network is ventilated. As I said, even the basement storage room has something like that. And we have 80% less than in the dressing room.

What could a decentralized ventilation look like?