Now after 3 months I have an update.. and another question.

So the indie has replaced the pcv valves, bit it didn`t change anything. The noise is still there and the engine error reappeared after driving for a couple of hours. So either it is something else or they made something wrong.

To summarize the issue:
As soon as the engine is warm, the noise as in the video linked before appears. The noise is gone when the engine oil filler cap is lifted. It seems to suck in air (neutralize a vacuum in the crank case) and then the noise is gone. Also, there is that hole under the vehicle where flexplate and torque converter are connected. When I bougt the car, the bung that belongs into that hole was missing. I`ve put a provisional bung in to cover the hole and that also makes the noise disappear. It also sounds as it would come from that hole or that area. The car also consumes oil, more than a liter per 1000km, but doesn`t seem to leak.

Any ideas about this? Could it be something different from the pcv valves? Is there a crank case ventialation system build in that chamber that is normally covered with the bung? How else could putting the bung in make the noise disappear?

The car is again at the indie at the moment, but he just called me that they have no idea.