As the Ext.chart.series.Pie3D.getItemByIndex() is just inherited from Ext.chart.series.Series, it would return a structure pointing just to one badly-positioned sprite. It should return as many sprites as its spritesPerSlice value indicates.

To fix that, basing a similar method override as its own Ext.chart.series.Pie3D.getItemForPoint() method should do the job. Basically changing the current response's sprite to point to the correct list of sprites suffice.

We have been notified about this issue a few months ago by one of our users and logged it ourselves after Ext.NET GitHub issue's #1646.