Assume that you have Clustered Columnstore Index (CCI) on a table in SQL Server 2017 or 2019. When you run versioned scans (such as Snapshot Isolation (SI) or Read Committed Snapshot Isolation (RCSI)), and if a "tuple mover" merge or "alter index reorganize" process is also running on the same table, you receive wrong results.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
This problem is fixed in the following cumulative updates for SQL Server:
Learn about the terminology that Microsoft uses to describe software updates.