iMovie not filling screen

Haven't used iMovie in a few months and I see some things have changed. I mainly take videos with my iPhone and put them together in iMovie without much editing. I haven't made any changes to what I usually do but now when I add my vids, they appear surrounded by a large black border. How do I turn that off? I've added about 15 vids to the timeline and all but one have this large border. Have no idea where the border came from nor how one of the vids managed to avoid it. See how the title appears outside the image instead of over it?