Claudio,
The workflow with model and layout teamwork projects separate is a common one. So this is not a problem.
Your problem may be the result of not sending and receiving from your model before you linked to a view from the layout project. I am assuming you are speaking of links to views and not links to files. Files can go missing, if the concerned file is on a local machine and not a computer visible to other machines.
Likewise the replacement of a linked file (like a pdf) that is local to one user could appear to have been updated by the local user, if the drawing's settings are for auto-update, but unless the drawing is reserved by the user the updated and subsequent send&receive drawing will not be sent to the server. Changes to unreserved drawings are never sent by ArchiCAD. Other users who cannot see the local file directly will see only the old file that had been stored in the project. For this reason I highly suggest setting your drawings to manually update to avoid this possible confusion. Manually updated drawings always have to be reserved for even the local user to see the changes. In this way it is guaranteed that the drawing will be reserved when the send&receive is performed.
If I haven't touched upon your issue, it might be worth investigating if you can reproduce it with a few simple steps.
Ed
Graphisoft Technical Support
