Failure of sister chromatid separation during meiosis ii would lead to

The reduction division or the meiosis  in which a single cell divides into four daughter cells. The meiosis shows the reduction division as the chromosome number reduces up to half in the daughter cells.

Sister chromatid separation occurs in the anaphase of meiosis. The failure of segregation of sister chromatid at Meiosis II will result in the formation of two normal haploid daughter cells. The one daughter cell will have the one extra chromosome whereas another cell will have one less chromosome number.