Using the Network tab of the Web Inspector, I was able to interrogate the images being served up on this page. Despite the filename (img_1913-jpg.5286282/) the image that is failing for me is being served up as a .webp file but the next image in the set is being served up as an .avif. That would explain why I'm not seeing it, as .webp is not supported on WebKit in Catalina whereas .avif is.
I thought there might be some browser sniffing going on in the script because in Safari the file is served as a jpeg and displays properly, so I tried chaging Orion's User Agent to 'Safari' through the Develop menu but it didn't help.
Strangely enough, if I right-click on the broken image icon and choose 'Open Image in New Tab' then the image is served as a jpeg in Orion and shows properly.
NB Sometimes the avif file is garbled but that's likely a separate issue.