Civievent custom data field duplicate fields in Edit
I guess the custom field is configured to use for Participants entity with Event name/event type/role set to any.

Solution for fix:


Upgrade CiviCRM to 5.15 or 5.16 because i can't replicate the bug anymore on latest version of CiviCRM.
Change the custom field config to use only Participants as entity instead Participants(Event Name), Participants(Event Type) or Participants(Roles).




Thanks

Pradeep