When you compile or run a query that contains a UNION operation in SQL Server 2014 or 2016, and the rowsets in the union contain lots of columns, a "Non-yielding Scheduler" condition may occur. Then, SQL Server generates a memory dump file.
Cumulative update information
The issue was first fixed in the following cumulative update of SQL Server 2014:
Recommendation: Install the latest cumulative update 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. We recommend that you download and install the latest cumulative updates for SQL Server 2014: