Wrong image link when sharing news item on Facebook

Hello,

I have a website with a news archive, where each item has a "share on Facebook" link (via the standard Contao syndication options on the article configuration).

When a news item is shared on Facebook, the teaser appears correctly on the user's Facebook timeline, but the accompanying picture (set via "Add an image" when creating a news item) does not. The reason for this appears to be that the wrong URL is sent to Facebook.

To give an example, the news item URL would be something like this:

Code:

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http://example.com/en-GB/news/items/Something

---

And the corresponding image would be at:

Code:

---

http://example.com/assets/images/0/PB255768b-4baa1df0.jpg

---

But the image URL sent to Facebook is instead:

Code:

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http://example.com/en-GB/news/items/assets/images/0/PB255768b-4baa1df0.jpg

---

It would appear that it gets turned into a relative URL under /<language>/news/items instead of an absolute site URL (i.e., starting with "/").

Incidentally, the image does NOT appear along with the teaser on the News page of the Contao site (Newslist module) either. I do not know if this is in any way related.

Any pointers as to what might be wrong, and especially, how to fix it, would be much appreciated. :)