Inspection shaft on property full

Well, there was a lot of local precipitation, so it is quite possible that the groundwater level has risen at your place.

Possibly also due to external construction work in the vicinity of your house.

I would assume the screed has to be removed and then one has to see further.
If the water stood ankle-high in the basement, a normal construction drying is simply no longer sufficient.

After the sewer cleaners were here today, they found that the drain pipe in the inspection shaft is positioned a bit too high. This means that some water always has to accumulate at the bottom before it can rise and flow away. So no blockage in the pipe. Works as designed.

In fact, they have now inspected almost all our pipes with the camera, and it was found that many stoneware pipes had shifted (partly severely, but mostly not quite that extreme). And one spot was broken, where shards and holes etc. were seen. That was exactly at the place where we have the most moisture in the basement. We strongly assume that we have now found the cause.

Unfortunately, due to the connection angle, they could not look into the drainage – the curve would not have allowed the camera. Too bad, because I still suspect that the drainage is damaged or even nonexistent in certain places.

that many stoneware pipes had shifted (partly severely, but mostly not so extreme). And one spot was broken, where shards and holes etc. were visible

An exchange of the pipes will be necessary soon, before the garden and terrace are finished. Given the expected amounts of rain, I would also install a channel as terrace drainage and connect it to the sewer. And create a slight slope away from the house around the house.