Try to move portal-core.war in /jboss/server/default/deploy then update the files. It should work, let me know.
Back from vacation.
Updating directly on the server does not work, even after I have moved it like you said. Also tried to undeploy and then deploy it again, but then I get this:
14:06:30,346 INFO [MainDeployer] Package: file:/jboss/server/default/deploy/portal-core.war/WEB-INF/ is already deployed