XMLExport ends with a null pointer exception

We export XML using XmlExport.startExport() in a script. During debug mode on the client it runs fine and creates an XML file of 75mb. When we run the same script in the same environment in scriptrunner on the sever, the script ends with a null pointer exception in XmlExport.startExport(). I am not able to get more details out of it. The script is very simple. Set some default and run the export.

We are using ARIS Business Architect 7.2.

Any idea?