Recently in Autodesk Vasari, I was attempting to run some wind tunnel analysis on conceptual masses. (3 total) My first run worked fine and I could adjust the 2D data slice perfectly. On the 2nd run I noticed that this was not the case, the 2D data slice kept on resetting! 
After some google searches I found that similar people have experienced this issue and there isn't a predictable cause or a definite solution. Below is a video showing my solution that worked for my case. (I have only tested this on conceptual masses so far.)