Cleaning company does not dispose of the garbage - Should the company be sued?

So, now about the craftsmen issue with me. The plastering company, which has actually been finished for a while now, has sent the final invoice. The invoices always go through the architect, who checks them first and then forwards them to me. Now, the plastering company has left a lot of rubbish behind. The architect has been talking and writing to the head of the plastering company for a while now, telling them that they have to dispose of the rubbish before the final invoice is paid and has also sent him excerpts from the VOB stating that it is their responsibility. The company refuses. The architect has now suggested deducting a flat rate for the disposal by an external company from the final invoice and informed the company accordingly. Response:

Good day,
we will let it come to a dispute because we have really been through a lot,
for example - discount additionally despite good prices
- we could not carry out the construction site in one go and therefore had problems on other construction contracts
- we disposed of most of the construction debris!
but never mind, do what you think is right and we will react accordingly.

It’s a pity that you surely now think what a bad company this is but put yourself in our position, we barely made any profit on the site because we kept the prices low.
It was the first construction contract we did together, if we do one again such things won’t happen anymore because we will pay attention then.

Great. Are they just bluffing now or what do you think? I really don’t feel like investing in lawyer fees for this mess. What would you do?
By the way, it was not agreed that the construction site would be carried out in one go.

I would do it as the architect suggested. Pay the remaining amount. Draft a letter with a note about withholding payment and setting a deadline for disposal within 5 working days. Then the final payment will be made. Announce that the remaining waste will be disposed of externally if the deadline expires. Refer to previous phone calls between the architect and the company. "As already stated in the letter dated..., it is your contractual obligation to dispose of the waste... etc." The remaining amount they want must then be claimed through legal action. I would definitely let it come to that. The tiler also does not get full payment for half the work.

I would too. I find the argument (apart from the wording) quite odd: "We miscalculated in the offer, so we decided to reduce the service afterwards." Next time, I'll try it the other way around. I'll only pay part of it because I realized afterwards that I can't afford the originally agreed price.

We are currently dealing with a similar issue. We obtained an offer in July from a company, and in August our architect gave the order (in writing). Now the company suddenly wants thousands of euros more. Because the offer was way too cheap. You have the advantage that at least the work was led by you and other trades can continue. I also don't understand how a professional can afford to do something like that. I would leave it up to you. You are in the right.. What could happen. He wants money from you. The other way around would be worse.

If the VOB was certainly the basis for this contract and it clearly states without any room for interpretation that they must do it, then I consider setting a deadline and then performing the work ourselves with offsetting to be correct.

But: legal advice does not hurt, even if you do not want to go to court.

Don’t understand how a professional can afford to do something like this.

Neither do I, but here I do also apply it to the architect: why did he choose someone he did not know yet?

I don't either, but I certainly also refer to the architect here: why did he choose someone he didn't know yet?

Here in southern Lower Saxony, it is such that you can be glad if someone takes pity and accepts a contract. Currently, most are well busy with orders. If I now only include companies in the tender with which one has experience, it quickly leads to a refusal. So even without a choice, enough trouble :-)