FeedWordPress: why are posts displaying thumbnail AND full-size image?

Here’s an example of the issue:
https://www.motivation.org.uk/pages/read-about-philip-%E2%80%93-now-driven-to-help-others/

I’m using the FeedWordPress plugin to pull posts from our blog site (https://blog.motivation.org.uk/) to populate the ‘latest news’ section of our main site (https://motivation.org.uk/). The issue is that the posts that FeedWordpress is creating display both the thumbnail AND the full size image.

I’ve tried using various RSS feed types, but now it’s set on RSS2.0. Not sure why this would be happening, and whether it’s a FWP issue or an issue with the feed generation on the blog site. If you’d like to see more examples, just click on any of the links in the ‘Latest News’ section at the bottom of this page.

Either way, I’d love to hear if anyone has advice. Thanks!
– Mickey