When using the CW source in my N9918A the output resets with every sweep of the SA. The source is in CW mode, not tracking or coupled CW. If I use settings to set a really long sweep time the signal is stable for as long as the sweep lasts. On my N9912A this does not happen and the CW source is stable and does not stop/start when a new sweep begins. Both FieldFox's have the older CPU and are running the latest 8.18 firmware.
One other issue as well - I connected a GPS antenna and turned on the internal receiver. I enabled "sync clock", the time was already within a few seconds so it was fine but after a few hours it popped up a message about not being able to change the clock by more then 6 hours, yet no time change was needed. I suspect this may have occurred when GMT time rolled over to a new day. I am on pacific time.