That means 'NX_FS_UNSUPPORTED' and happens when the file system is not supported(ntfs or ..) or any errors on the file system of the memory card or HDDs inside bridge pellet.
Note that, you need to disable "Show Video Clip during Copy" option at the setup for copying REDMAG.
Currently there are known bug in firmware which make error if you enabled that option.
If that is not the case, I recommend running 'chkdsk' on the Windows computer to check the integrity of the file system inside REDMAG or Bridge pellet according to the direction here.
Also, if you send us the LOG file inside bridge pellet to us, then we will be able to advice you more details about your problem.
Zip the 'NsbLog' folder and send it to us at firstname.lastname@example.org.