The cause of the issue is that the images on your website are being served with a relative path (../). Discourse is correctly adding the host name to the path, but it is failing to add a slash (/) after the host.
The issue seems to be happening here:
I can’t think of any cases where it wouldn’t make sense to add a slash after the uri.host if the src starts with a relative path. I’ll ask our engineering team to see what they think about making that change. It’s likely that we won’t be able to get back to you about this before early next week.