Frequency jump in the TEN-TEC PTO is not a new thing.
The ARGOSY suffered from the same problem. I believe that the
grease in the internal screw mechanism would get contaminated
with use and RF would cause the capacitance across the grease to
change and the frequency would jump 50 to 100+Hz.The solution in
the ARGOSY was to take the PTO apart and clean out the grease
and replace it with a higher quality grease. (silicone?)
With respect to backlash(?),there may not actually be backlash
but the apparent backlash may be a result of the processor
trying to lock the frequency before tracking back in the other
I had the same problem when I built a phase-locking oscillator
to "assist" my ARGOSY in stability.When changing direction of
tuning the phase lock circuit would sometimes "encourage" the
PTO to move to the next point(2-3cycles ) before turning back in
the new direction. If TEN-TEC are doing a similar thing with
the SCOUT then it may display what appears to be backlash.