Quick export knocks project out of sync.

I'll edit a video in premiere, then I'll do a quick export just to see how it looks in full res.

 Suddenly the exported video is anywhere from 12 to 36 frames out of sync, and when I go back to the project, it's out of sync by the same amount. As though I had been working out of sync the whole time, but it's wildly out of sync. 

Sometimes I'll spend 15 minutes fixing it, tnen I'll export, and it will be out of sync by exactly how much I adjusted it to fix it.

This happens to me randomly, but often enough where it's absolutely infuriating.