Conflict with Themify Builder

Hello, I’d like to bring to attention a conflict between WP Fastest Cache and Themify Builder (Front-End).

When clicking on Themify Builder on my webpage, it’s meant to bring up a visual builder which I’ve been using for some time now, although it’s now just stopped working!

What I did was, disable all plugins one by one until I found the culprit. The Themify Builder started working again after I disabled WP Fastest Cache (I’ve tried each Plugin I have, only 12).

The error message that Google Console gives me is as follows;

Uncaught TypeError: Cannot set property ‘post_ID’ of undefined
at HTMLIFrameElement.<anonymous> (themify.builder.loader.min.js:9)
at HTMLIFrameElement.e (jquery.js:3)
at HTMLIFrameElement.dispatch (jquery.js:3)
at HTMLIFrameElement.r.handle (jquery.js:3)

Any idea on how to get around this conflict? as I state above, this error only appears in the Google Console when WP Fastest Cache is active.

I really want to keep using WP Fastest Cache although I can’t do without Themify as that is what the website is entirely built with.

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