Teradata JDBC Driver returns the wrong schema / column nullability

I'm running an Apache Spark application that uses terajdbc4 to fetch data from a Teradata server.  It seems to be returning the wrong value for the nullability for many of the columns in the table.  I've found two scenarios at work:
1. If I use dbtable = "TABLE_NAME" all columns are returned with nullable = true (despite some not being nullable)
2. If I use dbtable = "(SELECT * FROM TABLE_NAME) as t" all columns are returned with nullable = false (despite some being nullable)
Is this a known issue with either the Teradata driver or the server?