i had a similar problem with a mp4 file that was corrupt, and not being able to find version 1.5 of grau anymore. i came up with this solution.
grau version 1.6 + (only does 50% of video for free version)
make 2 of the same video files and name them 1.mp4 and 2.mp4 this means you will copy video.mp4 in the same fold twice so you have two of them!
in DOS (Run: cmd.exe)
locate to the folder where you have the two video files
type in the command to merge the files together
copy /b 1.mp4+2.mp4
you will now see that 1.mp4 will be 400mb and not 200mb
now use grau video repair tool and it will do 50% of the file you merge. meaning you will get 100% video freee!!
Nice trick with some old dos commands.