Upfront Builder is giving WSOD

I'm having some issues with Upfront. After updating, I'm getting a white screen when I go to modify a theme that was created using the builder.

WordPress is at version 4.8, and Upfront and the builder are at the latest versions.

I've tried with all plugins disabled, and replaced all core files of WordPress. I've also tried rolling back to older versions of Upfront and the Builder. Nothing seems to make a difference.

Any help would be appreciated.