blueprint service registration-listener doesn't perform callbacks

a bean specified as a registration-listener of a service in blueprint descriptor is completely ignored, no callback occur. in other words service's registration-listener functionality is completely broken.
tested with many service configurations obviously blueprint schema compliant, also tried multiple listener bean callback method signatures fulfilling blueprint spec requirements.
btw services has been reliably running on smx <=5.3.1 (<= karaf 2.4.0)...