I finally had the time to update my website with the theme update, and I noticed it has a conflict with w3total cache, as this PHP error disappeared after I deactivated it? Do you know why this would happen? I would like to keep using this plugin, as it is the best caching plugin that works with my hosting.
Can you try reducing image size and uploading the it again? Did you already try to just delete cache? It might cached content. Do let us know how this goes.