I have a video file with 60FPS. When I add it to iMovie v 10.3.5 I can click share > file and I have option for example 1080p60 but as soon as I add audio track, I can no longer export it as 60FPS. Is it a bug or feature and I am missing some knowledge? If I merge the audio with video file into mp4 it works as 60 FPS without problem, although Finder cannot play audio but VLC can (unless I recode the audio to ACC).