Problem with Excerpts funcationality

I’ve got a problem occurring with the “Excerpt” functionality on my site.

Plugin version: 3.5.15

Summary:

When I enter an excerpt on the book page, it saves and appears to load just fine. When I view the page, I get the first few bits of the excerpt. That initial part is working properly.

When I click the “Read More” link, the “more” of the excerpt doesn’t appear and the “Read More” link stays the same instead of changing to “Collapse”.

The page appears to try and load as as second set of buy links appear at the bottom of the page.

You can see an example of the situation at this link: http://amyknupp.com/amyknupp/book/sweet-spot/

Things I’ve tried:

-) Custom CSS – I have a bit of custom CSS in the theme editor portion of the site. I’ve removed all of that, saved and reloaded the page. It doesn’t make any difference.
-) I have an Excerpt Plugin installed to create excerpts in blog posts on the site. I’ve deactivated that (no change) and even uninstalled it (no change).
-) Browsers: I’ve tried it in Chrome (current version) and Firefox (current version) with no change. It behaves the same. In Safari (v 10.0.2) it tries to work. You click the link and the rest of the excerpt appears, but in a few seconds, or if you try and scroll, it vanishes again. Almost as if it’s trying to work but then reverts. No change on reload.

Things I’ve done recently to the site:

I’ve recently migrated to a new host. The migration went off without a hitch and I’ve not seen any other problem. The folder structure of the site changed slightly, but that’s it and nothing else seems to be affected. I’ve updated the Permalinks settings multiple times (just in case) with no luck.

I’ll be happy to send along any info you might need.

Thanks in advance for your help!

-Justin