I was going to check the TF on each stage of PMC's servo.
Unfortunately, I couldn't find the floppy disc drive, so I slide the sliders (gain, RF power) around. When I add more RF power (from 1V to 7V) to 21.5 MHz EOM, the oscilaltion subsides*.
How sad. Stop using the floppies and get one of the GPIB-Ethernet converters from Dmass. You can download the python scripts from the 40m wiki.