[shauli]

Originally Posted by HamletEagle SortCustom1D(and other natives probably) uses qsort to perform the actual sorting. http://www.cplusplus.com/reference/cstdlib/qsort/ Documentation says the order of equal elements is undefined, this is why.

Thanks, that explains it.
So basically if i'll do 'return 1' for equal items it will work as I expected.