This occurs when the web service call contains special characters (e.g. ë, ü etc.) and the java "file.encoding" property is not set to "UTF-8". If you run using the Modeler this is set by default and when running without the Modeler in the default "application.conf" file the line "wrapper.java.additional.2=-Dfile.encoding=UTF8" has been added in the template to prevent this error from occurring. However if you're using an older template of the "application.conf"-file this line could be missing. Adding this additional java parameter will solve the problem.