Solved this by using the newest SQL Server JDBC Driver. A had an old one from 2012. Now i downloaded and used the newest JDBC 4.2 from https://www.microsoft.com/en-us/download/details.aspx?id=11774 (sqljdbc_4.2.6420.100_enu.exe -> sqljdbc42.jar) and it started working. I could even revert the default schema changes for the SQL user.