ERROR: vtkMultiBlockDataSetStructure does not match. You must use CopyStructure before calling this method.

Dear Experts,
my reader read many files by parallel and all data will be converted into vtkPolyData then add into vtkMultiBlockDataSet, it works OK, but sometimes, paraview report below error:

ERROR: In paraview\VTK\Common\DataModel\vtkDataObjectTree.cxx, line 377
vtkMultiBlockDataSet (000001D72A9B4E20): Structure does not match. You must use CopyStructure before calling this method.

Why it pop this error?
How to solve it?

Best Regards,
Sharon