Wrong thumbnails showing

Hello,

Our client has noticed that some of the thumbnails that appear for the related posts are not the correct images. We took a look at one of her posts and see that it has a featured thumbnail set, however, the thumbnail that is displayed in the related posts area is very incorrect. Also, the displayed image is nowhere mentioned within the post. Would you happen to have any idea on what could be causing this?

– Vita

https://wordpress.org/plugins/contextual-related-posts/