To turn off the DJI Osmo Pocket 3's ActiveTrack feature off:
Double-tap your subject on the screen to turn on ActiveTrack, tap outside the tracking frame or press the joystick once to turn off ActiveTrack.
Next go to the DJI Mimo app, frame to select the subject and turn on ActiveTrack tap “×” in the upper right corner of the tracking frame to stop tracking.
It's important to note, ActiveTrack is not supported in Low-Light, Panorama, Slow Motion, and Timelapse modes.