PosHold, loiter not stable it drift

ArduCopter Copter 3.5
1
  • 4010 850kv
  • 1150 prop
  • 1.5kg AUW
  • no wind
  • HDOP 0.5
    i calibrated ESC, accelerometer, Compass.
    my s500 not stable it drift not hold point.

what i wong?

log bin
http://upfile.mobi/MuU66HNcWPi