Signature of prefabricated house under reservation with right of withdrawal

... just finds it nonsense to be pressured and threatened with a price increase that the head office doesn't even know about...

That alone would be reason enough for me to take action, but definitely not to sign.

Everyone should be ringing alarm bells that something is not right.

So: call the head office and ask if the seller is making up the price increases himself.
If that is the case, turn to another home builder or seller.

That would already be a reason for me to take action, but definitely not to sign.

I also refused to sign for such a construction company.

I also refused to sign with such a construction company.

Ditto. That is a no go.

I also refused to sign with such a construction company.

We too have once declined this tactic with thanks.

Exactly the same pressing behavior happened to us as well, at first we were treated very well and from the 3rd appointment onwards the seller only pressured us.
At that time we were still missing an appraisal, whatever they said you can withdraw from the contract at any time, etc.... We said we wouldn’t sign anything before the appraisal and suddenly this super special mega price was only valid for 2 more weeks, etc... by then it was basically already over for both of us, the final rejection came with the contract and the scope of construction services, that was a disappointment.

Our current construction company never pressured us and despite a really catastrophic start into the building adventure, there was never any pressure, on the contrary!
For me, that is what makes a good and reputable company.

Don’t let yourself be pressured, this is way too important a decision for that.

Best regards