Igor with multiple axis in a graph

I like to draw a plot with several panel in a graph, without arrange them in the layout, which waste some space between the individual graphs.
If I draw a 4(row)*1(column) plot, I would use the default axes (Left and Bottom) for the bottom panel. For other panels, I would create new axes, e.g. L1,B1, L2, B2, L3, B3. "L" indicates left axes and "B" indicates bottom axes.
After I set the draw areas for Left, L1, L2 and L3 axes, I usually make the B1, B2 and B3 cross the responding left axes (L1, L2 and L3) at zero. It works very well at this point.
However, If I save the experiment and reopen it later (such as two days), the positions of B1 and B2 would change, even they are set to cross L1 and L2 at zero. And now i can not make it go back to the "perfect" setting.
Do you guys know why this happen. PS, I'm using 6.22A version.
Thanks.