Symptoms
Higher than expected number of single row Columnstore rowgroups may be generated for Columnstore bulk insert when both the large page allocator (Trace Flag (TF) 876) and the scalable Columnstore bulk insert features (TF 11064 and TF 11068) are turned on.
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
Resolution
This issue is fixed in the following cumulative update for SQL Server:
Each new cumulative update 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:
References
Learn about the terminology that Microsoft uses to describe software updates.