Possible Causes:
Drone power distribution board overheated.
Overheated battery or bad battery.
Troubleshooting Steps:
Put a known good battery into drone and see if error message goes away.
See if an update is available for the drone or battery. If so, update.
Replace Power Distribution Board on drone.
Replace Spray module if replacing Power Distribution Board does not work.
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.