You need to go to the settings in the goggles first:
Enter the menu of the goggles, and then go to Settings > Safety > Advanced Safety Settings > Emergency Propeller Stop.
Then, try pushing the control sticks on the remote controller as follows:
Push both control sticks on the DJI FPV Remote Controller 2 to the bottom inner or outer corner.
Note: Stop the motors mid-flight in an emergency only, such as when the motors are stalled, the DJI Fly app prompts that the aircraft is malfunctioning, or a collision occurs.
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