HitTest not consistent when hovering over Doughnut chart

[User (Legacy)]

We execute the hittest method during a mouse move event to determine if the 

user is hovering over a series in the chart (or in the case of a Doughnut, 

we expect a hittest value of 4 when the user hovers the mouse on the top 

side of a 3D doughnut chart). 

If there is 1 Doughnut on the screen (this does not happen as frequently 

when there are multiple doughnuts on the same chart), sometimes the hittest 

returns 4 and sometimes it returns 0, even though I hover the mouse on the 

same general top area of the chart doughnut slices. 

To repro, you need to create a doughnut chart with just one doughnut, and 

its easier to reproduce if the chart  application is maximized. Hover the 

mouse slowly around the top side of the doughnut chart area and notice that 

at times when the hittest should return  4, it returns 0. 

What's the problem? I get consistent return values of 4 when the chart is a 

PIE rather than a Doughnut. 

Thanks Frank, 

Gretchen