ᐅ Incorrect installation boxes used. Who is responsible for the resulting costs?

Hello everyone,
we have the following problem...
We ordered 19 recessed ceiling spotlights in the prefabricated ceiling on the ground floor from the shell construction company. We want to control everything via DALI.
One spotlight was charged at €83. This price included the housings and the installation.

Now to the problem...
THE COMPLETELY WRONG HOUSINGS (Kaiser 1227-55) WERE INSTALLED!

One housing alone costs €2.14! The diameter is 60mm (2.4 inches).

I could not fit any spotlights into these housings, so I said, "Remove the ceilings and redo them!"
This was not done. The ceilings were simply laid on top. I had no say in this, for whatever reason.
The shell constructor promised to find a solution. I agreed, on the condition that the full price would definitely not be paid!

A core drill hole of 170mm (6.7 inches) was made, and the correct housings were inserted and somehow adjusted (??)...
Complete mess! On top of that, the openings for the “new” housings were terribly modified. They want me (a layperson) to close the gaps.
The spots are partly misaligned and not flush with the ceiling surface as they should have been at the factory.

To somehow ensure alignment, I bought new front covers (about €6 each) to at least achieve a decent result.

The point is, they insist on the full amount, saying they did not earn anything and actually lost money.
The fault clearly lies with the shell constructor.

How would you handle such a situation? Would a 50-60% deduction be reasonable, or would you say a full 100% deduction is justified?

I really need advice on this matter.

Do you have a general contractor or is the project managed through separate contracts? Do the plans clearly indicate the installation boxes to be installed without any doubt?

Vicky Pedia schrieb:

Do you have a general contractor or is it a direct contract? Was it clear from the plans which recessed lighting housings needed to be installed?

This was done under direct contract. Based on the spot lighting plan provided by the architect, the diameter of the spots was known, and the housings were to be selected accordingly.

So they are not specifically listed in the scope of work?
Are they documented in writing anywhere else?
At least the required diameter, or whether with or without a tunnel?

guckuck2 schrieb:

So, are they not specifically listed in the scope of work?
Is there any written confirmation at all?
At least regarding which diameter is required, or whether it should be with or without a tunnel?

This was communicated verbally. It was a small mistake on my part not to document it.
It was discussed with the general contractor (project management) and then passed on to the structural builder.

lin0r87 schrieb:

This was done verbally. That was a small mistake on my part not to document it.

Then you have already admitted fault yourself. Verbal agreements are worthless. You will have to bear the loss yourself.