Having my new drone for some days now I was facing a corrupt video file today. I guess it got corrupted when I turned off the drone before ending the recording. According to some information from the DJI forum this seems to be a known issue for some (maybe all) DJI drones.
Even though the .mp4 file seems to be created properly on the SD card, beside the video file itself you can find a .trinf and a .avc1 file.
Inside the DJI forum I found out that I'm not the first person who had this problem. But luckily I also found a solution for this issue inside the forum. You can use the tool djifix which can be found here. Inside the forum it is mentioned that the homepage seems to be offline sometimes.
Using the tool is pretty easy. Simply put the tool and the corrupt file inside a directory and run the following command:
djifix name-of-video-file-to-repair-including-any-.MP4-or-.MOV-filename-suffix
Afterwards you will have a .h264 file. If needed this file can then be converted to .mp4 afterwards using ffmpeg.