I believe I found where the issue resides at least and a workaround. This is a problem with XY graphs in general when trying to programmatically control the cursor position. Somehow, the software goes looking for the nearest point instead of the identical point and has some sort of issue with its search algorithm. Switching from attempting to match position to copying the cursor 'index' completely cleared up the problem I was having. In the particular application I'm working on, the four graphs have identically spaced data on the X-axis, so this solution should work fine for me.