[amsat-bb] Satpc32 calibration Help

[Don]

Yaesu GS232B and G5500  did calibration in manual, all is OK.  180 and 450

  Using  Satpc32 with Yaesu Gs-232 rotor interface selected. Settings 
2-60-N-0 selected as options...... Stored.   Quit and restarted 
program.  Go to Rotor  control and manually  set elevation to 90 degrees 
and azimuth to 90 degrees.  Execute  settings. Results are about 12 
degrees low.  Used the correction buttons to bring up the rotor 
directions to 90 degrees and saved the corrected values. Quit and 
restarted program.   Back to rotor control, and send rotor  to Park 
position  (both set to 0 degrees park position) Both the elevation and 
azimuth go to about 12 degrees - not zero. Try to correct values by  
zeroing, save and quit. restart and send back to 90 degrees again result 
in low readings.
  What am I missing?  Thanks Don.