If you experience your quad drifting off in one direction or a Toilet Bowl Effect(TBE), where the quad hovers in one spot but drifts in a clockwise or counter-clockwise pattern.The main reason for this problem is due to incorrect compass calibration. The secondary reason is that the vibrations from the motor may be shaking the compass.
The following Official DJI NAZA Manual details how to calibrate and solve the drifting and TBE.
Page 11, details compass calibration.
Page 29, fixing the TBE.