Joe Obbish shows how you can recreate the error described in KB 4462481:
Consider a query execution that meets all of the following criteria:
1. A parallel INSERT INTO… SELECT into a columnstore table is performed
2. The SELECT part of the query contains a batch mode hash join
3. The query can’t immediate get a memory grant, hits the 25 second memory grant timeout and executes with required memory
The query may appear to get stuck.
Click through for Joe’s demo. The fix? Update to SQL Server 2017 CU11.