strange small black bars appear in video when uploaded to instagram

[philb60559546]

at some point last year, maybe after a certain update, when i create a video in premiere pro, and upload to instagram, i get a strange black bar on the right side.

the bar isnt in the video, just in the thumbnail.

if i take a video with my phone,  and edit it on the  phone, and upload it to instagram, there isnt any problems.  if i take that same phone video, and put it into premeiere pro, make zero changes, and export it under the same settings at in the original phone video (making no changes at all), the black bar is back.

premiere pro is somehow saving the video in a way that instagram doesnt like

ive tried rolling back to PP 2021 version 15, same thing happens.