Fair enough, but the principle of operation for the YIG self test might be similar.
On my spectrum analyzer, after failing the YIG test everything except for the frequency still works. The frequency is off by about 50 MHz when I feed in a 1 GHz signal. I don't know if it is the same on your analyzer or not.
There is an RF switch at the input which switches between the N connector on the front panel and a calibration signal (which is at -30dBm I believe). The RF switch is broken on my device I think, since the input of the switch has a DC voltage of -5V when the switch is on (which definitely shouldn't happen). If your spectrum analyzer works mostly but has a frequency error and fails YIG calibration, I would look for the calibration signal / RF switch. Of course, since the devices are different there is no guarantee that calibration is done in the same way (perhaps yours has a sampler or prescaler to measure the frequency).