I must be missing something but how is this an exploit? No code is running.
You have just corrupted the film so of course it will stop. All it prooves is that the movie player has no error checks built in as it should not freeze the 3ds.
Do the same to any picture / mp3 or anyother format...
My supercard sd on my gba micro.uses goomba colour alpha 6 and no option to increase the screen size.
Why do it anyhow, it would be stretched and distorted.
Rich