Hello chippie,
Yes, the issue can be resolved by resetting a device to its factory default settings. Since the backup file contains static lease configuration including the name of the lease, there is a chance that a router becomes inaccessible after the backup upload.
We are planning to implement static lease validation into forthcoming firmware releases in order to prevent this from happening again in the future.
Please note that this issue occurs due to the fact that RutOS is based on Linux distribution that does not support special symbols in system configuration files.