Incorrect image displays sometimes in Main Product Page

Needing some help please. Haven’t been able to find out what is happnening.

New site, updated an older one. Sometimes when opening main product pages a different image is in there. It is the same ‘different image’ though each time. If you refresh, the correct image is there. When checking the images in the set up, it is the correct image. It’s happened to me a few times but have also recieved messages from customers. I can’t find anything on this. Has it happened to anyone else? Know what could be causing it?

The link above now shows the correct image for me.

The page I need help with: [log in to see the link]