Iframe not loading images

I use the Gravity Forms iFrame addon to embed some of my forms to other sites, however recently it has stopped uploading the images included in these forms. Everything else is loaded, just not the images - does anyone have any ideas?

Can you share a URL for the page on your website where we can see the Gravity Forms form pulled in with the iframe?

It used to load images fine, and I can’t think of anything I’ve changed. I’ve also tried it on another website I own, with a different host, and I get the same issue

It doesn’t work in the source location either:

https://pocket-tests.com/gfembed/?f=63

That probably means it’s not related to the iFrame plugin. There is quite a bit of invalid HTML in this page (if you view the source): view-source:https://pocket-tests.com/gfembed/?f=63

Thanks for your help. It’s strange, because the images load when I click form preview…
I’m guessing it could be caused by a plugin conflict for example?

The same form loads images when embedded into the parent website via shortcode: https://pocket-tests.com/example-level-test/

Update: Just in case anyone else gets this - disabling EWWW Image Optimizer solved it.