What do you mean, non-invasive dna has no results, hemolysis?

Is it because of the quality problem of blood collection tube or because of shaking or high temperature during transportation, which leads to the rupture of red blood cells? Because the detection of peripheral free fetal dna is non-invasive, although red blood cells do not have nuclei, white blood cells do. Hemolysis shows that cells are lysed, and white blood cells may also lyse and release dna, which will lead to inaccurate results of maternal dna pollution.