In this database there are documents with different forms. When a document is opened (web) the URL is always:
https://server/database.nsf/$$OpenDominoDocument.xsp?documentId=4DFBCA...&action=openDocument
The Domino server opens the document in the XPage which is assigned to the corresponding form for the document with this unid.
It works fine. But the problem is that when you use a RPC to get some information from CSJS this doesn't work. You get the error which I noticed.
Have you further questions?