I think we should put them back in if this is the outcome. We had a session array holding onto the old hostname.
I manually run the rebuild_poller_script and poller_reindex_but the problem persists.
Accessing the database I discovered a strange behavior in the poller_item table.
The problem is only present on devices that where present on the old 0.8.7g installation.
If I create a new device (same configuration of an old one) and I change the "hostname" attribute, the modification is immediately propagated to the poller_item table on all rows.
Configurations from newer versions cannot be restored to older versions.