Netgear Nighthawk M5 Restore Backup

Hi,

I've just bought a Netgear Nighthawk M5 from Telstra to use with a USG3 and found that restoring backups does not appear to work.

After customising the device I save a backup via the GUI and then perform a factory reset.  After a reboot and reconnecting I restore my backup but none of my customisations changes return.

The export.cfg (aka configuration backup) is plain text so I can see that my changes are saved, but they are not restored.

Whats the point of being able to restore a backup if all the settings are ignored?

Some insight on what the expected behaviour would be appreciated.

Cheers