We are also on FMC 6.4.0.4 and cannot add TAXII source. The GUI attempts the POST to FMC API /api/tid_ui/v1/domain/e276abec-e0f2-11e3-8169-6d9ed49b625f/taxiiconfig/discoveryinfo. HTML error 500, with this details: {"error":{"category":"FRAMEWORK","me...