Hi I’m having the exact same issue. Just updated to 4.15p4 and it’s a project that was created pre4.15 and ‘opened as a copy’ initially in 4.15p3.
Any enum switches I have get reset to “New Enumerator N” (in the switch only) each time I open the project, just as in 's screen cap above. If I create a new enum in 4.15p4, however, it’s fine.