We use to receive the below error in our listener log. There are no errors in terms of connection to the DB from the client side since we can see other sessions in ACTIVE in DB doing the operations.
<txt>TNS-01153: Failed to process string: (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=bbdd-ppz000-01.srv.osi)(PORT=50072))(CONNECT_DATA=(CID=(PROGRAM=)(HOST=__jdbc__)(USER=))null))
NL-00303: syntax error in NV string
Follow the note 1364680.1, which says this can occur due to inclusion of multiple JDBC jar files in the classpath and that should be removed.