ffmpeg -f lavfi -i sine -f lavfi -i testsrc2 -t 10 -c copy video_first.mkv
ffmpeg -i video_first.mkv -i video_first.mkv -map 0:a -map 1:v -c copy video_second.mkv

In preferences, select only "Tiled Center Column". video_first.mkv will work okay, but video_second.mkv will crash, even though the audiovisual data is identical, just the track order is different.