I have faced the same issue while drawings X-sections. But when i categorized the data in different patterns finally i came to know the reason.
Remember while categorizing the data, first of all you need to place your negative values and then place your positive values, in this way the right bank stays right and left bank stays left.
e.g: https://www.dropbox.com/s/o0bx592ad95depj/Screenshot%20%2866%29.png?dl=0
