CRM-18328 Custom fields do not show on Register Event Participant

Upon upgrade to 4.7.4 the custom fields that we setup for Register Event Participant do not show up on the New Event Registration form anymore. The custom data set we are using is enabled, "used for" is set to "Participants", Type is "Any". The fields show up on other screens but not on the Register Event Participant entry form. I tested this in the CiviCRM public sandbox (4.7.5) and the same issue happens. Please help asap. We have an event coming up soon and need these custom fields to track critical event data and are unable to enter or edit data because the fields don't show up on the entry form.