Tornado chart negative value bars including

I have an issue ragrding showing negative values in a Tornado Chart.

I have calculated a difference [MeasureA]-[MeasureB] and want that difference to show in a tornado chart. 

If result is positive->show that value
If result is negative >show that value

Right now I sometaimes have negative bars and sometimes only a vlue but now bar - how come?

Is there a solution?