Finally found the reasoning behind this.
After the move to Cloud hosting, from Shared hosting, I had updated my DNS records. However, I never updated my IPv6 record.
This wouldn't normally be an issue (and it explains why 99% of websites/services had no issue scraping/using my site) but Facebook appears to prioritise IPv6 over everything. So it was using my IPv6 record which was pointing to my old server and an old version of my website. Hence, it was pulling in no information for the page.
I'm surprised it was still linking to the new page after we manually put in the image and title when posting to Facebook.
I spotted this after my Share hosting plan was officially cut off today, therefore deleting my old website. The links began showing a 404 error.
Hopefully this can help others, as I've seen a lot of people with a similar issue but no solution. Update your IPv6 record as Facebook uses it!
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