Page Builder seems to be corrupted

I was happily using page-builder on my theme. The last thing I did was to drag a prebuild block from it’s position to somewhere near the top. Then when I saved, the browser gave me a 500 error, both on the wp-admin, and on the homepage (I was editing the homepage).

Did I corrupt the template somehow?

This template is the first one in the list (which I presume is why the admin side is failing).

The website is here: new.agape-cp.com

When I loaded into Firefox (for the first time), it helpfully gave a clue when I tried to “inspect page”. Everything after is missing.

I can’t “view source”. I have a screenshot of the Inspector panel; I can send it if necessary.

Please help :( I loved editing with this builder, and we need to put up our new site very soon.