This issue occurs under relatively rare circumstances. And this issue continuously occurs even after you install Cumulative Update 8 for SQL Server 2014.
The issue is fixed in the following cumulative updates for SQL Server:
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. View the latest 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.