TOPIC: [SOLVED]was working

Richard - as just stated in your ticket, the issue seemed to be your incorrectly setup checkbox custom field.

People... watch the video tutorials! Especially for custom fields. If selection limits and such are not setup properly, it will cause you issues.

In my defense - it was working for dozens of tests and real registrations.

Nothing changed with how selection limits work. What happened is that over the course of your tests, you probably hit the incorrect limits of each checkbox option, causing the field to basically become dead. The way it was setup WOULD work... AT FIRST... but not for long.