Botched plastering of the wall or proper execution

The wall construction in the stairwell shows bulging joints at transition points between floors. I wonder whether this is technically necessary and cannot be done differently, or if the problem is related to poor workmanship during construction.

The side walls in the stairwell are made of 100mm thick gypsum blocks with tongue and groove. These were leveled with approximately a 0.5 mm layer of plaster, then covered with a fleece wallpaper. The fleece wallpaper was treated and the bulges were repaired with fine plaster. A Q3 finish was supposed to be achieved. The entire surface was then treated against chalking again and painted over. At the joints between the floors (bulging areas), only a perforated metal profile is visible, which is used in drywall construction for corners.

When cutting into the wallpaper, the entire plaster crumbled off, and the paint separated from the wallpaper. I am attaching a few pictures here and would appreciate your feedback. In my opinion, this is still subject to a complaint.

If this isn’t botched, then what is? Complain, set a deadline, and hope that the botcher doesn’t come, but his colleague does.

logo botch, get rid of it........................?!?!?craftsman should come

Sure that it was a craftsman and not a [Fleischereifachverkäufer]? It looks catastrophic...

uuh, that was more than clear, thank you very much! At least I don’t regret cutting open the wallpaper now. Could someone maybe give me a tip on how it should have been done properly? I thought of an expansion joint, but I am not the expert in construction.

Why an expansion joint? It looks like the thin layer of putty does not adhere to the substrate. So, for example, the wrong material was puttied. I have already seen on construction sites how gypsum plaster was used for puttying. Why is the Alueckschiene there?