Same issue.
Chose the "Delete World Save" option and Save/Restarted and it does nothing.
FTP'd into the server and manually erased the world files, but the server just regenerates the exact same map data I had already erased?
As if it's pulling it from a backup or not actually erasing the files when told to via FTP.
Trapped in my world and unable to start fresh, which is a giant problem.. hopefully something gets fixed soon.