Deceased in KLAS is equivalent to Deleted in PIMMS. Once a patron record is deleted in PIMMS, it cannot be resurrected. The work around right now is to add a new patron record and merge the old patron data in it.
Once you change a patron to deceased, you should not do any other updates to the record, like removing subscriptions or changing addresses. This will generate a resend error because the patron is marked as Deleted in PIMMS. Do any kind of record cleanup prior to making the change of status.