Why doesn't my msbuild scenario work

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MSBuild

Why can't I build my Project with dependencies?

What I have tried:

In my Solution I have a Project (Project Main) with dependencies to four other Projects (Project A, B and C). If I execute the command

msbuild [Project] /p:configuration=release

on Project A, B and C, MSBuild will create my bin/release files as i expected.

When I execute above command on Project Main, MSBuild will build Project A, B and C too because of dependencies. But on this point it fails on Project C with following error:

Confirm that the <usingtask> declaration is correct, that the assembly and all its dependencies are available, and that the task contains a public class that implements Microsoft.Build.Framework.ITask.

I don't understand this. Why does the Building not work when I build it as dependency.
If I don't provide enough Information, please inform me. I am still very unexperienced in Terms of MSBuild and don't know all processes of Building.