iMovie app doesn't show clear picture
I'm new to iMovie. I just want to edit my mpeg-4 movies to remove some extra material. When I drag & drop the movie into the app, it show up with a green tint and the upper right pane is all pixellated. The movie plays OK, but this makes it hard to edit. Why does it look this way?
MacBook Pro 15″, macOS 15.0