Hey Mark,
I don’t personally know or have SiteOrigin’s PageBuilder, but I did find the following support thread on WordPress.org where a member of the SiteOrigin team mentions that there is an option to enable the PageBuilder for custom post types – check out the second reply from the user “Greg Piday” on this thread: https://wordpress.org/support/topic/can-pagebuilder-work-with-posts-and-custom-post-types#post-4425453
There just so happens to be a setting for that. Navigate to Settings > Page Builder and select all the post types you want to use Page Builder with. Posts, pages and custom post types are all on offer 🙂
I hope that helps – if you find this option, enable the builder for Events and any other events-related post types you’d like. “Venues” and “Organizers” are the other Events Calendar post types.
If you do not find this option, or have issues getting the page builder to work on single events, I’d recommend reaching out to SiteOrigin’s support team and explaining the issues there. Keep us posted, as well, and hopefully we can help 🙂
Cheers,
George