[QUESTION] Segfault when exposing class member variable with buffer protocol

I want to expose the following class, specifically I am interested in the *voxelBlocks:

template<class ITMVoxel>
    class ITMLocalVBA
    {
    private:
        ORUtils::MemoryBlock<TVoxel> *voxelBlocks;
        MemoryDeviceType memoryType;

    public:
        inline TVoxel *GetVoxelBlocks(void) { return voxelBlocks->GetData(memoryType); }
        inline const TVoxel *GetVoxelBlocks(void) const { return voxelBlocks->GetData(memoryType); }
        int lastFreeBlockId;
        int allocatedSize;
  }

GetData(MemoryDeviceType memoryType) looks like this:

/** Get the data pointer on CPU or GPU. */
inline DEVICEPTR(T)* GetData(MemoryDeviceType memoryType)
{
	switch (memoryType)
	{
	case MEMORYDEVICE_CPU: return data_cpu;
	case MEMORYDEVICE_CUDA: return data_cuda;
	}

	return 0;
}

Reading the documentation, it seems that the following buffer protocol should suffice:

  PYBIND11_NUMPY_DTYPE(ITMVoxel, sdf, w_depth);  // sdf, w_depth are uchar and short

  py::class_<ITMLocalVBA<ITMVoxel>>(m, "ITMLocalVBA_ITMVoxel", pybind11::buffer_protocol())
    .def_readonly("allocated_size", &ITMLocalVBA<ITMVoxel>::allocatedSize)
    .def_buffer([](ITMLocalVBA<ITMVoxel>& v) -> pybind11::buffer_info {
      return pybind11::buffer_info(
        v.GetVoxelBlocks(), 
        sizeof(ITMVoxel), 
        py::format_descriptor<ITMVoxel>::format(), 
        1, 
        { v.allocatedSize }, 
        { sizeof(ITMVoxel) }
      );
    })
  ;

However, when I try to access it, the program crashes (with a segmentation fault).
Does anyone have a clue? Help would be much appreciated, my Master thesis depends on it.

Start with the shown ITMLocalVBA::GetVoxelBlocks method and the def_buffer lambda, then reproduce the buffer access while checking the returned pointer, format, shape, and lifetime. Done means the exposed buffer can be accessed without a segmentation fault and represents the intended voxel blocks; no repository file or test is named in the issue.