I have a project in my iMovie - a 60 minute video of a wedding my wife took on her iPhone. Anyway I set it to music, etc and after when I try to move the finished project to a thumb drive in order to give it to the bride..It will copy have of it on the thumb drive then I get an error message that says it cannot complete it. I know I am doing something wrong..it is in mp4. May be it just does not like me. lol. Should I try saving it in another format? Or just may be my thumb drive is bad. I have an iMac Retina 5K, 27-inch, Mid 2015 again not that has anything to do with this problem..I believe. Thanks in advance. Be kind to this novice of iMovie.