Possible Causes:
Drone Cable Distribution Board overheated.
Bad Spray Module.
Troubleshooting Steps:
See if an update is available for the drone or battery. If so, run an update.
Replace Cable Distribution Board.
Replace Spray module if replacing Cable Distribution Board does not work. In rare cases, the Power Distribution Board and/or the Aerial Electronics Module might also need to be replaced.
IMPORTANT: If the drone hit a power line or was involved in a crash, DJI recommends replacing both the Spray Module and Cable Distribution Board at the SAME time because if there is a short, it would take out a newly replaced board as soon as its installed.
Prevention:
This issue can sometimes be prevented by good heat management of the drone and batteries. See our article here on Tips On How To Keep Batteries and Drones Cool To Prevent Forced landings.