Hi Lucas
Maybe it is because the fields are only collected for group members and you do not have group members exported ?
Go to Events Booking -> Configuration, look at Export Registrants Settings tab, make sure Export Group Member Records config options set to Yes, then try again to see if it works ?
If it still not solve the issue, please submit a support ticket sending us super user account of your site so that we can check it directly on your site for you
Regards,
Tuan