I visited your post and the image now seems to be displaying correctly on first load, but not upon subsequent loads.
Here’s a screenshot of the post loading correctly for me the first time I visited that post today:

Have you added any custom JavaScript or jQuery to your site? If so, that may be causing a conflict.
In addition, could you try disabling your plugins one by one to test if any of them are the cause of the issue?
Let me know how you get on with those troubleshooting steps.