Symptoms
Assume that you use SQL Server 2017 Analysis Services (SSAS) in Tabular mode. When you try to edit the tabular model, you cannot change the isAvailableInMdx column property to False.
Resolution
This fix is included in the following update for SQL Server:
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Each new build for SQL Server contains all the hotfixes and security fixes that were in the previous build. We recommend that you install the latest build for your version of SQL Server:
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
References
Learn about the standard terminology that Microsoft uses to describe software updates.