String to file download on premise

Hi,

My goal is to create a CSV file with the StringToFile java action and then download it with the common MX activity.

When I do this locally there is no problem, CSV (with custom name: 'Detailed_invoice_' + formatDateTime([%CurrentDateTime%],'yyyyMMddHHmmssSSS')
+'.csv') is downloaded and I can open it.

When I deploy this on premise at the customer I get the following message:

The file '' could not be found.-------- com.mendix.webui.WebUIException: File id or guid parameter should not be null
    at com.mendix.webui.requesthandling.FileRequestHandler.retrieveFileDocument(FileRequestHandler.scala:210).

So I do create it with a name and dont know where this message is coming from.

Does anyone have any ideas where this is coming from?