I answered the support ticket opened on the same subject. I would like to ask you continue our discussion in only one thread to avoid duplication. Thank you for your understanding.
Here is a quote of the answer:
If the error is thrown only when the dimension is added through UI, then the unique name returned from the Mondrian cube differs than the one you've added programatically. Could you further investigate the difference?
In general, the widget requires the full member path (in the case of a dimension - the full path of root member). If it is not provided, then the widget will perform incorrect request, the cube will return incorrect result and an error could be thrown. In some cases, the Mondrian cube sets optimized unique names (only [Calendar] for instance instead of [Date].[Calendar], which is not correct for the widget).
The PivotDataSource supports binding to XMLA1.1 standard (MS SSAS) and if Mondrian returns something different (in most cases different setup) and then the widget will not work as expected. Please verify that the Mondrian cube behaves similarly to the MS SSAS.
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