Incorrect installation housings were used. Who bears the resulting costs?

Good day everyone,
we have the following problem...
We ordered 19 ceiling spots for the raw builder in the filigree ceiling on the ground floor. We want to control everything via Dali.
One spot was charged at €83. Included are the pots and the alignment.

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

One pot itself costs €2.14! The diameter is 60mm.



I couldn’t put any spots in there, so from my side it meant: "Take down the ceilings and redo them!"
This was not done. The ceilings were just laid on top. I had no say in this, for whatever reason.
The raw builder promised to find a solution. I agreed, on the condition that the price definitely will not be paid in full!

A core drill hole of 170mm was made and the correct boxes were installed and somehow adjusted (??)...
Total crap! On top of that, the tunnel of the "new" pots was modified so terribly. I am supposed to close the recess too (layman).
The spots are partly not aligned and not flush with the surface. (As it should actually be at the factory.)




To somehow ensure alignment, I got new front covers (about €6 each) to still get a decent result somewhere.



The point is that they insist on the full amount because they didn’t make any money and actually lost money.
The fault definitely lies with the raw builder.

How would you deal with such a matter now? Would a deduction of 50-60% be okay, or would you say to deduct the full 100%!?

I really need advice on this matter.

Do you have a general contractor or is it a separate contract? Could the installation boxes to be installed be clearly identified from the plans?

Do you have a general contractor or is it a single contract? Could the sockets to be installed be unequivocally identified from the plans?

This was done under a single contract. Based on the spot planning with the architect, it was known what diameter the spots would have and the pots were to be chosen accordingly.

So they are not specifically listed in the scope of services? Otherwise somehow documented in writing? At least which diameter is needed, or whether with/without tunnel?

So they are not specifically listed in the scope of services? Otherwise fixed in writing somehow? At least which diameter is needed, or whether with/without tunnel?

This was done verbally. That was a small mistake on my part not to record it. This was discussed with the general contractor (project management) and then passed on to the shell builder.

This happened verbally. That was a small mistake of mine not to record it.

Then you have already admitted your guilt. Verbal is worth nothing. You will thus be stuck with your "damage."