While you might believe that you have an error in WordPress, the actual problem actually is on facebooks end. When they already have an image, you need to force a rescrape (iirc) via their Open Graph Debugger(?). facebook caches images of various sizes by Url. Meaning that if you already served an image, they already have it on their servers and refuse to download. You now have two options:
- Rescrape with facebook tools
- Provide a different image on a different url
Whatever seems simpler to you is what you should do.