Andoird P - How to join mp4 files splitted by the camera

I've done multiples videos larger than 4GB with my Pixel 2XL installed with Android P. The camera as splitted my video in 2 files from continuous shooting. In all cases, the first file is readable but, for the second, I can only see the lenght of the video: Is there a way or a tool to join these files or to repair the second one ? I've already try a binary copy with "copy \b" and "cat", a join with ffmpeg -f concat and an append with avidemux without success.