When you duplicate an enum, the value names of the enum do not copy over, instead they are renamed as New Enumerator 0, New Enumerator 1, etc…
Thank you for submitting a bug report. I have reproduced this issue and logged a report for it here Unreal Engine Issues and Bug Tracker (UE-39324) . You can track the report’s status as the issue is reviewed by our development staff. Please be aware that this issue may not be prioritized or fixed soon.
The bug is still marked as unresolved but it seems to be fixed in 4.15.1.
Thank you for the notice. I have tested myself and was also unable to reproduce the original issue. I have updated the report for this as well.