Duplicate values are being suppressed in Jasper bar chart.

Question

I have a Jasper bar chart with occasional duplicate names. In the report customizer class I can see all of the expected data inside the JRChart's datastore, but there is only one value in the final chart.

Simple example - I have two items called "a" with values of 1. I would expect to see two items in the chart labeled "a" with bars that extend out to 1. But I only see one of them.

Any ideas on where to start looking at this? This seems like a fairly obvious use case.

Thanks