If you are using Premiere Elements 13/13.1, I know of no way to change the established project settings except by starting a new project.
The Adobe party line is that you cannot change project settings once they have been established in your Premiere Elements project. For Premiere Elements versions earlier than 13/13.1 I have described a way to do this. The way is based on editing the Notepad document for the saved project project file (.prel).
What were your specific export settings and what was your player?
My export settings were 1920x1080p 29.97fps M2T AVCHD and I played the file in Windows Media Player. But I ended up manually copying down all of the times for the clips and made a new project with the same numbers. So the problem has been solved the hard way.
Thanks for the update. Sorry that the new project was necessary. You did well making the transition from problem project to new.
However, you may have gotten into some trouble with your export settings. But, at least that can be corrected in the export of the new project and should not require starting from the beginning in yet another project. I am suspecting that your export is 1920 x 1080i 29.97 "M2T AVCHD" instead of 1920 x 1080p 29.97 "M2T AVCHD".
You appear to have used Publish+Share/Computer/AVCHD with the M2T H264 1920 x 1080p24. If you say that your export is 1920 x 1080 29.97, then you would have had to go under the Advanced Button of the p24 preset to customize the preset to 29.97 instead of 24.
But, now for the unexpected under that preset....if you use Frame Rate 24 frames per second, you have progressive settings. But, if you change the Frame Rate to 29.97 under the Advanced Button of the preset, you have interlaced settings. In the latter, note the fields for Upper or Lower for Field Order. That is interlaced video. Interlace video has fields, progressive video does not. And, if you do the export and read the properties of the export using a properties read out program, you confirm interlace and not progressive export. Confirm in project....
Can you use the MP4 H.264 1920 x 1080p30 preset instead?
Please review and consider.