Just did another backup-restore to a new box from v13 to v15.
Both old and new boxes were brought fully up to date, modules and RPMs and the Backup/Restore Module on both were brought to Edge. (v15 box already had the latest module).
Everything went smoothly EXCEPT I had to (again) manually setup voice mail for all extensions. Not critical, but the module is getting there. Maybe there is something in v13 that won’t allow a voicemail/extension setting restore to v15?