Hi, James.
Sorry you’re experiencing this.
Is this a WP_DEBUG message you received? If yes, please provide the full stacktrace and a description how to recreate this issue (what steps to take, what pages to visit).
If you need a refresher on WP_DEBUG:
Please enable WP_DEBUG and WP_DEBUG_LOG and share any debug messages you see while editing widgets, using the WP Customizer, changing tickets quantity, navigating your site’s home page, events page, single-event pages, and any other of your site’s pages relevant to this ticket.