Column chart values do not stay vertical?

Hi,

I have a Line and stacked column chart, when my sliders ar set somtimes I get vertically 0 to 5 as I expect (see below)

...if I change my sliders that set other info in the chart see how 0 is at the same height as 2, 1=3 and 2=4. All I want is to keep the vertical values on the left and above each other so this chart makes sense.

Thanks,

Dan