Premiere Pro Video Files Automatically Shifting

I'm editing in Premiere Pro 2019. My sequence and edit was working perfectly, so I exported and while playing back the export the video files were shifted but the audio stayed in place,. The film was out of sync because of this. I played it back again in my project sequence and it worked just fine, but continually was not exporting correctly. I turned Premiere off and on again (thinking it needed a reboot for the export to work) but then my sequence played back just as the export did. It shifted all of the video files. Is there any way to fix this? Hours of work have been automatically undone.