Does anyone have any idea what could be causing this issue

The holighted Cell Value should be the "Sum" of the groups "Items" but its total seems to be the same as the Items under Material even though there is no data in that Group for the Price Field

I've also included the code I wrote to calculate the totals for the Price Line. It only appears to happen if the entire gruop has a zero total

If I remove the PartName grouping the issues gets solved.

Inside of ds_AggregateMeasure

if (e.MeasureDescriptor.Name == "Price")
{
decimal total = 0M;
decimal count = 0M;
foreach (object o in e.Items)
{
var item = o as FrBudget;
if (item != null)
total += item.Price;
count += 1M;
}
e.Value = total;
e.Handled = true;
}