Suggest you obtain a standalone USB 3.x drive and use it as an intermediary step to backing up.
On page 44 of the manual its says "The following file systems for external drives are supported: ext2, ext3, ext4, FAT32, exFAT, NTFS, HFS Plus." First, plug your USB drive into the LS520 and from the format drop down list select FAT32 or NTFS for a laptop with a Windows OS. Dismount the USB drive from the LS520 and plug it into your laptop then perform your backup to completion.
Using NAS navigator 2.91 find your IP address and using a web browser use it to log into the NAS control panel. Create a folder for use with Direct Copy. Log out. Plug your USB drive into the LS520 and wait till both front lights turn white. Within 60s press the red function button on the back panel just once. A front light will start blinking and will stop and go out when the job is finished. Move your LS520 backup from the Direct Drive folder to another using cut and paste. Job Done.