"Unexpected error - Internal server error" happens when download quarantined file from Symantec Endpoint Protection Manager (SEPM) after upgrade (or newly install) SEPM to 14.3 RU6.
This issue is fixed in Symantec Endpoint Protection 14.3 RU7. For information on how to obtain the latest build of Symantec Endpoint Protection, see Download the latest version of Symantec Endpoint Protection.
To work around this issue, install "Microsoft ODBC Driver 17 for SQL Server (x64)".
CRE-13350