Facets results is sorted incorrectly then there are more then one sort processor enabled.
Results are sorted with last processor.
That's is because all processors in build stage are running by in self and sort processors rewrite previous results.
All sort processor's callbacks should be applied for result item pair. And the first value which is not equal 0 should be returned to apply sort.
Maybe we need new stage - sorting. After build stage run sorting with enabled processors.