Hello, i have an apparently stupid question for you, is it possible to see in real time, for an DJI assistant, the serial number of the gimbal currently installed inside the drone and if someone has changed it? (Model Mini SE) I've an horrible sensation about my drone, I've selled it and now the buyer is telling me that it doesn't work properly... and it was perfect, it's really strange, because there is the error 40021, and everywhere online they talk about a block by an unauthorized replacement.
Sorry for my bad english (and the stupid question).

I do not know if anything is available via the assistant 2 ....but......
If you go to the website
https://www.phantomhelp.com/logviewer/upload/
and scroll down the page you will find instructions concerning how to retrieve the flight logs from your phone.
Note that if you were using an Android phone then the location in the phone where the logs were stored changed so check one location and if it is empty then check the other location.
When you locate a log upload that log to the webpage and then download the csv of the log. Open the csv and check columns

IB, "RECOVER.cameraSn"     &     JD "DETAILS.cameraSn"  (from a pre app version log of a Mavic Mini )
or
EL "RECOVER.cameraSerial"   & EX "DETAILS.cameraSerial".    ( from the log of a mini 2)
or similar names
I do not see gimbal serial numbers recorded.

If the drone is returned and will NOT start its motors then you will NOT be able to check a log from the returned drone. The logs are created ONLY whilst the motors are running.......BUT..... from memory I think the camera serial number might be shown in the "About' section of the app. I would need to check that and to confirm whether or not the serial number shown in the log normally matches the serial number, if it exists, shown in the app.
I do not know if the SE had the camera serial number is on a label on the outside of a camera/gimbal, I have not seen one on my Mavic Mini or Mini 2.

The above said, physically swapping the camera and gimbal means the drone has to be almost completely dismantled and is a fairly major task for a bit of fraud. There are, from memory, 1 or 2 paper seals over screw holes near the mouth of the battery compartment that would almost certainly have to be destroyed to open the drone to enable the camera to be swapped.

Hi, fans28c369ae. Thank you for reaching out and we're sorry to read about your experience. Do you have the drone back? Regretfully, you will need to send it to our facility for them to check the SN of the gimbal. The error code 40021 indicates that the gimbal IMU data is not matched. You may try to calibrate the IMU by following the steps below:

1. Please go to Settings-Control-Gimbal Calibration.
2. Please go to Settings-Safety-IMU Calibration.

If the error code doesn't go away or if there is an error after calibrating the IMU please consider sending the unit in for a proper diagnosis.  You may submit an online repair request through this link: {https://repair.dji.com/repair/index}. If you need assistance with creating a ticket, you may contact DJI support at https://www.dji.com/support. We understand that this is not the answer that you look forward to, but this would be the best thing to do in this situation. In addition, warranty service can be claimed depending on the result of the Damage Assessment. Your kind understanding is appreciated and thank you for your continued support.