403 number appearing behind displayed image

I have a strange 403 error appearing behind my displayed image. I recently saved over an old site with a new site that was built in a different account/domain name but on the same server (we have a reseller account). has anyone seen this before or can anyone advise how to get rid of this message? It only appears when I click on the images, not when they’re displaying within a post.

Eg: https://www.ooi.com.au/portfolio/melbourne-facade-etchings/#/gallery_7370/2