Have had this issue several times. When I pull an unedited mp4 file into the tool, the video and the audio basically turn into a complete mess. The audio is no longer synched with the video, sometimes random periods of black screen with audio but no video, etc. The unedited mp4 file plays just fine in any number of viewers. I have done some searches but cannot find anything that helps. Anyone who can help me out here - would greatly appreciate, thanks.