Assume that you use a Multidimensional instance of SQL Server Analysis Services. After you ProcessUpdate a dimension, the Multidimensional Expressions (MDX) LastChild function may return incorrect result.
This problem was fixed in the following cumulative update for SQL Server:
About cumulative updates for SQL Server
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Article ID: 3183686 - Last Review: Jan 17, 2017 - Revision: 4
Microsoft SQL Server 2012 Service Pack 3, Microsoft SQL Server 2012 Service Pack 2, Microsoft SQL Server 2012 Analysis Services, Microsoft SQL Server 2014 Business Intelligence Community Technical Preview 2, Microsoft SQL Server 2016 Service Pack 1