After editing a 20 minute film and sharing it to my HD files, the resulting m4v file has some funky striped transitions. Why? They do not show in the time-line when played.
MacBook
Pro, Mac OS X (10.7.5), OS is El Capitan 10.11.6
Sounds like the transition did not render properly. Try deleting the transition and reapply it. If that doesn't help open iMovie holding down the command and option keys and delete preferences.
