When the device boots up, the system will apply the configuration named "startup-config.conf" on running partition. Different partitions may have different configurations. (It means each partition has its own configuration.)
How can I download the configuration from standby partition?
Make sure "FTP" service is enabled on the device and access the device by FTP.
After all, folders are listed, you can find the folder named "standby_conf".
All of the configurations are saved in this folder. You can download the config file directly.