I made a project in WMM consisting of 200+ short clips from movies synced to music. Watching the project in the preview window, all the edits are timed precisely and cleanly.

However, after saving the project to my computer, I see that every clip in the project lasts a tiny bit longer than they do in the preview (tenths of a second at most) causing the entire movie to now be out of time, with unwanted frames popping up causing the whole project to be borderline unwatchable.

Surely there's a solution to this problem? I can't imagine that the preview always shows an inaccurate representation of the final product? I've made similar montages before and never had this issue.

I'm using WMM 2012. All of the video files in the project are MP4.