background picture shown image being based64 after removing the plugin

Hi there,
First I’d like to Thank you for creating great plugin for WP community.
I have a question.
After removing the plugin, one of my shown picture shown up itself with base64 encoded form.

I am not sure why is that… can you please help me?
Here is the screenshot: https://prnt.sc/12cv47b
Thanks,
Q.
P/S: The image is rendered from the_post_thumbnail();

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