Hey all,
The upper and lower fan on M300 seem to be running fine, but the RC shows avionics warning upper fan stalled and doesn't let drone takeoff (ready to fly). The problem sometimes goes away after multiple restarts of the drone but is very random and is preventing a lot of flights.

I wanted to know if this is a firmware or hardware issue and what can be done to fix it?
It looks like some other people may have received this error after the latest firmware update
https://forum.dji.com/forum.php?mod=redirect&goto=findpost&ptid=235129&pid=2419146

I'm on the latest firmware for all components

Below are the images of firmware version and the error obtained. Let me know if more information is needed.

This is a common error with the fan module. You should send back to your dealer

I am also facing the same issue that it shows the of "Aircraft overheated. Return to home or land. Power off aircraft and wait for temperature to return to normal" & also  "Lower fan error. Land promptly > and check whether fan is stalled or making strange noises". These error always showing after 10 to 15 min of flight completed
How to fix it.
Below I shared the image of error showing.

Hi friend, I'm having the same problem, it started today after the new update.