Hi, I have several videos (*.mp4) saved in my Dropbox. Using the menu on the right, I can successfully save the files as *.mov, *.mp3 and *.wav. However, when I try saving the file as *.m4a it doesn't work. Loading appears at the bottom of the screen. Then Automatically saving your file as audio appears.... but it goes on forever and never finishes. Can you please help?