Streams videos not working when embedded on web page (using embed iframe code)

Hi -

We are seeing problems trying to use the embed code to embed videos on our Streams on webpages.
Videos that are on Streams (which play fine in Streams, or using the direct link), will not fully load/play when using the embed link on a web page on are intranet. (I just see the spinning circle, trying to load the video)
The issue is intermittent, meaning the videos do load/play occasionally, but very seldom.
Internet Explorer is the one browser where the videos will load/play sometimes, other browsers (including Edge) fail at all most or all times. I need it to work in Edge (at least).
I have double-checked and the videos permissions are set to "Allow everyone in your company to view this video".
Please let me know what I can do to fix this.

Thanks!
-Tom