Windows are smaller than in the building application/work plan.

By the way, you can also tell the proportionality by the fact that these few centimeters were not noticed before.

Rectifying defects must always be proportionate. This is probably not the case for a window replacement over 6cm.

The classic also because there are always different plans and one craftsman gets version 1.0, another 2.0, and the third 2.0a.

Mostly also because the client or lady decided differently at short notice or had a change on site.

I was at the house almost every day, yes the driving was annoying, but it was worth it. We also had the wrong parapet height on 2 windows, we noticed it right when the masonry was done and it was immediately corrected. Just like the passage between 2 rooms was suddenly floor-to-ceiling instead of normal like a door. Pointed out, corrected, done. Socket positions... yes, almost all of them were correct. The almost was then corrected during chasing. So yes - it's worth showing up frequently there. And to talk and ask. Friendly but firm. Write mobile phone numbers clearly on the wall in the shell as soon as it’s big enough for that. It will be used – so it was used for us.

Every house is a prototype and not an industrial product planned from start to finish.

I agree with you, but I also believe that houses (with early dry stone walls) have already been built since 9500 to 8200 BC, so despite changes, it should gradually work out. If one completes a three-year apprenticeship in their trade and works in the field for years/decades, I think it is not an impossible demand. I do not want to make myself unpopular here, but I still do not understand the industry. After the success/failure of building a house, I hope to be wiser; I consider myself a (limited) learning system.

...
Basically, every plan should say: "if older than 14 days, then actively ask for validity confirmation before execution".

This is the kind of thing I mean when I mention that I don't understand the customs in this industry. Even though in your example I would rather assign the responsibility to the client. You (as a non-expert?) see this sensible solution option, but why is something like this not implemented? There should be many approaches to achieve defect-free / less defective construction.

Mostly also because the client or mistress has decided differently at very short notice or had a change on the construction site;

The most prominent example is BER, where it is/is going the same way. Many plans and many client wishes after everything was approved and construction had started.

You (as a non-expert?) see this sensible solution option, but why is something like this not implemented? There should be many approaches for defect-free/less defective building.

Because it means a lot of additional bureaucracy. The solution approaches are the foreman, the site manager, the expert, and as the last instance the client himself. Despite these 4 supervising bodies, there are no defect-free houses. Anyone from construction will tell you that.

It's just complex. And lots of pressure in the [Kessel].