[ abandoned]Weird memory-leak when using a (unmanaged) DLL

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Hi, I'm using a DLL written in c++ (unmanaged).
Using this DLL I'm observing a massive memory-leak, which could be located to the unmanaged HeapMemory (using .Net Memory Profiler).

After doing some tests I figured:
Using the DLL from a console-application, which is just console-printing the information recieved via the CallBack-Functions the memory usage is constant.
Changing it to an WindowForm application and just registering empty CallBack functions the memory usage is constant.

When using the CallBack-functions to create/update objects the meory-leak is present.

Does anybody have an idea/solution on such a problem.