vtkQuadraticQuad does not persist cell attributes on clip
vtkQuadraticQuad breaks down clip solution for 4 quads. However vtkQuadraticQuad::InterpolateAttributes does not initialize local cell data for 3 of 4 quads - only first get initialized.
should be
this->CellData->CopyData(inCd, cellId, [0, 1, 2, 3]);