Server error 4.04 or 4.13 when uploading files

When we try to upload data the above message appears. IIS is configured to port 80. When the URL is changed to e.g. 8080 and the process is kicked off again, it does work. Is this a configuration error? It cannot be a permission/right issue, since then I would expect to receive an 5.xx error. What to do? (het mag ook in het Nederlands overigens....). Many thanks!
1 answers

In order for file uploads/downloads to work, you need to proxy the /file url to the mendix application, just like you're probably doing right now with /xas.