Second iframe doesn't render; plus junk text - how to troubleshoot?

[amca01]

My blog has been completely still and untended for over a year; I'm just getting back to it now. I have a new post which has two html pages, each displayed in an iframe, as in:

 #+BEGIN_EXPORT HTML
  <iframe width="620" height="620" style="border:none;" src="/page_to_show.html"></iframe>
 #+END_EXPORT 

One of them displays perfectly, the other doesn't show. Well, it shows under localhost:1313, but it doesn't show when I deploy it to my server with an rsync command.

Another issue is that I'm getting some junk at the beginning and end of the post, when displayed. At the beginning there's some material related to the tags:

cs", "geometry", "jsxgraph"] draft = false +++

(the first tag is "mathematics"); and at the end:

[//]: # "Exported with love from a post w

I have no idea whether these issues are from hugo, ox-hugo, org-mode, or some mixture. But I'd be happy to have any advice of how I can troubleshoot them.

Thank you very much.