Registration page allowing people to register without answering all required questions

[VSGFC]

Hello, 

We have dozens of people who are registering for an online meeting who have somehow bypassed one of the required custom questions. 

When we generate a report, it shows 'No response', which isn't one of the answer choices. 

My colleague and I both have tried registering and it will not let us confirm and register without answering this question. 

Does anyone know what's happening and how to quickly fix it?