When using the sort (spreads), and having some equal values in your spread, the ‘Former Index’ pin seems to ‘random’ the sequence off the slices that are double.

In the forum I found some people got the same problem, but cannot find the solution! someone can tell me how did you solved this?

as björn pointed out, this is a feature of the sorting algorithm. i guess our algorithm is not ‘stable’. where stable means, it keeps the order where ever possible.