I am hesitant to set up a YouTube account just to do a little testing.
I was hoping that someone running Win 10 would be able to try the non-youtube function to see if they get the same unusable results.

If it's a Codec issue, then it's a BIAB issue.
BIAB should include, and use, a working Codec when you click the "Show Video File" button, or at the very least, inform you that you don't have the correct Codec and offer to send you to the appropriate website to get it.

Thanks all !!
LLOYD S