Why does the 8590 Series Spectrum Analyzer fail during the internal frequency self calibration stating, FM SPAN SENS FAIL?

This failure will only occur during the internal frequency self calibration. There are two coils on the 1st LO or YTO known as the FM coil and the Main coil. The FM coil is used in spans less than or equal to 10 MHz. To receive this error, a linearity or tuning problem was detected in firmware when the span was 10 MHz and lower. The Analog or Counterlock board are the most probable causes of this failure.