MOV had actually been automatically added back in via the transition feature. It still wouldn't export completely and I went to the section that it stopped exporting at and discovered that when certain transitions are in place, they add back in parts of slides even if they have been clipped, so a previously clipped PPT. MOV files which I had gone through and manually clipped shorter to remove that first blank frame from each one. This was not an issue before the update but now it halts export. MOV files are imported into iMovie they come in with a BLANK FRAME added to the beginning of them. The new iMovie does not seem to be able to work with PPTs that have been exported as. Here is what I believe to be the problem everyone. Hopefully thats the problem resolved but I have like the slowest upload connection so won't know for deaf for a good couple of hours. Imported an older video I had shared on you tube and split the intro out of that to finish my new video and. Tired to mix that file again to the video and guess what?.Failed message reappeared So even though I couldn't see any glitch in the intro video something had gone wrong. IT SHARED THE WHOLE VIDEO TO FILE !!!! WOOHOO Took out my intro video (the part that wasn't playing video but just sound) and then tried to share again to file. Re watched the whole original video ini move and couldn't see any glitches but the problem must be within the first 4 seconds.right? Then checked my desktop to find the file had been created but when played noticed the sound was there but no video and after 4 seconds this stopped all together. I shared the video to file on my desktop and waited for that lovely message to appear again telling me it had failed. I thought it was a bug in the update but tried a few things to see if I could resolve the issue.

Imovie export mp4 not working