I have an N9912A running A.08.18 firmware (original CPU) and believe I have found a source level bug.
If the unit is powered up to the spectrum analyzer and the source is enabled it will be around 25 dB down in level compared to what it claims the output should be. It will say the level should be between -2 and +10 dBm but it will really be around -18 dBm. The attenuator works correctly but the level will always be low. However if you start the CAT first or switch to the CAT and then back to the SA source level will be correct.