XMLCoder encode invalid data type in JDBC adapter

After SQL-insert commands I get the message in the log-file:

XMLCoder encode invalid data type: com.wm.app.b2b.server.JDBCConnection.

The SQL-commands are executed well but the error-message is confusing.

envorinment: IS 4.7 with corefix 8 and service release 8.

many thanks for any hint