I cannot reduce the RBW of my E4402B below 1 kHz (with a span of 150 kHz and center frequency of 1.24 MHz) It experienced a memory reset and the firmware was reloaded last year and I guess this is the first time I have tried to use a lower RBW since that all happened. It has shipped with options 1AX, 1DN and 1DR. It would seem I may have lost option 1DR (the tracking generator appears to be working fine). What do I need to do to get the enhanced RBW option working again? S/N is MY41441731.