I found a better solution (but its still just a temp. workaround!) . I just put the result calculation into the never ending while loop.
In this way PlayerController->GetInputMotionState starts working in a ‘normal’ way.
Just replace AndroidProcessEvents in LaunchAndroid.cpp with the following code.
You can find the code on my UE branch. [1]: https://github.com/hallifaxx/UnrealEngine/commit/f0ee135e747aff6201962d9d50b13105c730e382