Hi there,
The issue just appeared after I updated the domain details and took this site live. it was previous on a development domain name – not sure if that has anything to do with the issue.
That would be my guess. Make sure the image file URL paths are also updated to the live site as well.
Your hosting support might be able to help to identify and correct the issue as well.
The theme itself cannot cause an issue like this.
Hope this helps 🙂