Export and Share Quality - Adobe Premiere Elements 2020

Hi.  I am having an issue with the resulting mp4 file from doing an Export and Share.

Once I've completed creating my video, I click on Export & Share, Computer, Resolution and choose HD 1080.  I am creating this mp4 file for my YouTube channel, and to store on my google photos account/site.

My timeline contains both photos (jpg) and video files (mp4) taken on my Google Pixel 3 phone camera/video camera.

When I look at the video files on my phone, they look fine and smooth.

But, when I add them to the Adobe Premiere Elements 2020 project and export to the resulting .mp4 file, many of the video files are "jerky".  By that, I mean that when I am doing a slow pan say - from right to left, the pan is "jerky" and not smooth. 

When the mp4 file, located in the timeline is run and shown in the "preview area" above the timeline, it looks pretty good and smooth.  However, when I look at the finished product, that same segment (mp4 file) of the exported movie is not.

Any thought?

I appreciate your help...