Gypsum plaster does not hold, too soft - tear it out yes/no? Suggestions?

@schwarzmeier Sorry, I apparently misunderstood that at the first appointment. At the last meeting with the expert, Bösteinhaus, the plasterer + an employee from Knauf (actually regional market manager but according to his own statement also an expert for plastering work) a different picture emerged again. Knauf employee, plasterer and Bösteinhaus say the plaster is okay, the substrate was prepared incorrectly. The expert also thinks that maybe the priming/sanding was done incorrectly in addition, but without an expert report that won't be visible. I have to let everything sink in first.

Against the issue with the sinter layer speaks for sure that our painting company, to my knowledge, sanded the surfaces beforehand - but despite repeated written requests for a statement, they have unfortunately remained silent on that so far.

In the end, probably only a complete expert report with test drillings and laboratory analysis will provide clarity.