Yesterday I imported a movie into iMovie that I wanted to chop up and re-arrange but when I export it the exported movie is choppy/stuttery, although the audio is fine. I've tried exporting as mp4 and .mov, and tried with compression and without. I've checked the frame rate and the original is 23.98fps as is the exported movie. Does anyone have any idea why, and how I can fix it? I'm running a 2017 MBP Touch Bar with 2.9GHz i7, 16GB RAM and 1TB SSD. I recently upgraded to OS Mojave and this is the first movie I've exported using this, don't know if this has anything to do with it. Any help would be appreciated.