Paving not even and firm - what helps?

The sand is no good, it has to be removed, sand consists of round grains and cannot be compacted. Maybe it works for a few days/weeks but then your craftsmen will be long gone and you will have the problem.

It has turned out that it is not sand - as I amateurishly called it - but so-called crushed sand. This is split that is simply a bit smaller. I apologize for the inaccuracy.

The brechsand is compactable.

You can dismiss the idea that the gravel or crushed sand under the stones gets washed away as an urban legend, otherwise our houses would also eventually stand crooked, since the same gravel is underneath (no crushed sand). However, our paved areas are bordered by curbstones, so nothing flows out, at least no substructure. What can happen with gravel in the joints will happen... the stupid ants carry it away over time... what color is the leveling material under your stones and what color is the joint sand? Crushed sand is gray for me, gravel yellow. I compacted an additional parking area with a 60 kg compactor from Bauhaus, everything works, you just can’t compact a 30 cm layer all at once. But nothing else than what you yourself have already suggested works, either remove everything and start again or do patchwork...

It also looked great until the small plate compactor came. After that, it was crooked and uneven.

But normally it looks more crooked before compacting than afterwards, not the other way around...

I see it the same way: not compacting the ground to a stable state, but rather laying the paving between two compaction treatments, seems to me to have been the main error in the process here.

The construction worker was here again today and we looked at the situation together. The pavement consists of 2 parts. One is the sidewalk connection with small stones. That is a disaster. He wants to redo it completely. It’s only about 6m².

The rest are the parking spaces for the cars. They are paved with large stones. These are naturally bumpier. He will now compact the entire surface again. In the process, he should try to smooth and stabilize it a bit. That would be enough for me if it works. Well, we’ll see.