So, I posted my issue over here: https://stackoverflow.com/questions/64110444/react-app-w-react-router-within-a-third-part-iframe-issues-with-pushstate
BUT that issue deals with a scraper, I think.
NOW, I got to thinking, is it really "just an iframe" that is causing such a problem, so I put my site INTO a friends website iframe... and it works perfect. NO ISSUES.
So, the first issue (see link above) must be doing something that is generating that error. Any ideas? Could it be them trying to scrape the site? Is this a nginx issue in that I need to add that domain? Or perhaps i can update helmet()?