Windows 10 Version 2012 after exporting it adds in extra frames, which ruins my movie.

I'm editing an existing movie by chopping it up and putting it together in different orders. It looks great in movie maker. However when I export, on many clips it seems to take the first few frames from the next chronological scene and put them in. I've checked in movie maker and I haven't missed these, they get added in export. This makes my clips unusable, as it flickers another image for a few frames then gets back on track, but thats way too distracting. Also the extra few seconds this adds up makes my audio out of sync. Anyone have any ideas? Thanks