Right of retention and refusal to accept, whose fault?

I really can't imagine a transnational planning template at a German building authority.

In case of doubt, there is a German rubber-stamper.

In case of doubt, there is a German stamp expert.

... with the corresponding professional liability insurance - at least for the objectively ascertainable questions of fault. Unfortunately, I see the OP here *ahem* "not without considerable own contribution to the unsatisfactory result" ;-)

Ok I understood it but thanks anyway for your answers.

It has been prohibited in Germany to install these since at least 2017.

Where does that come from? If done properly, you can manage with a KG installation. Depending on where you build, an MSH is not state of the art.

Where does that come from? If done properly, you can live with a KG entry. Depending on where you build, an MSH is not state of the art.

I also googled it right away, because at my place only KG was used except for drinking water (there it was one of those blue pipes). Apparently, in 2016 some supply associations agreed to only allow house entries that are gas- and liquid-tight (single- and multi-service house entry). However, I could not find any references to legal regulations. And if the supplier does not specify anything, it is also possible otherwise. And even in KG, you can install seals.