"undocumented error" when adding 3rd parent level to matrix -

For SQL 2016 RTM, in both Report Builder and Report Designer, I can add a matrix using the wizard that has 3 levels on each axis. Product into Subcategory into Category on Rows and City into State into Country on Columns with Sales Amount in the data section.
If I try to do this from scratch in a blank report, when I add the 3rd group (Category - in the example above), I get "Undocumented error." In the details it states "The RDL structure of the tablix named 'Tablix1' is invalid.
I tried it on 2 different computers.  Also, I created one successfully with the wizard, deleted the Category group and received the same exact error when I tried to put it back in.
I opened a Connect item for this, but that may take a while and I need to know now if this is just me, a new "Feature" in SQL 2016, or something else.
I'm trying to recreate a report that I used for a demonstration in 2008R2, 2012, and 2014 and I never had this problem before.

Query I used for one of my datasets:
SELECT        DimGeography.City, DimGeography.StateProvinceName, DimGeography.EnglishCountryRegionName, DimProduct.EnglishProductName AS Product,
                         DimProductCategory.EnglishProductCategoryName AS Category, DimProductSubcategory.EnglishProductSubcategoryName AS Subcategory, FactInternetSales.SalesAmount
FROM            DimProductSubcategory INNER JOIN
                         DimProduct ON DimProductSubcategory.ProductSubcategoryKey = DimProduct.ProductSubcategoryKey INNER JOIN
                         DimProductCategory ON DimProductSubcategory.ProductCategoryKey = DimProductCategory.ProductCategoryKey INNER JOIN
                         FactInternetSales ON DimProduct.ProductKey = FactInternetSales.ProductKey INNER JOIN
                         DimCustomer INNER JOIN
                         DimGeography ON DimCustomer.GeographyKey = DimGeography.GeographyKey ON FactInternetSales.CustomerKey = DimCustomer.CustomerKey

Ann Weber