Rsync not working between RN528X and RN212

rsycn is a protocol different than SMB, authenticating is required. But before, the rsync server on the destination NAS must be enabled and configured. Once done so, start with the [Test Connection] offered - for some reasons, it exists.

- Per NTGR, authentication is not required:

https://kb.netgear.com/29741/How-do-I-back-up-data-between-two-ReadyNAS-OS-6-systems-using-the-backup-manager

- Yes the destination NAS is enabled for RSYNC, as noted in the original post:

"Rsync is enabled in the system settings, and Rsync is enabled specifically on the Pictures folders of both NAS's as well (right click on Pictures folder, select Settings, click on Network tab, make sure Rsync is ON and Read/Write is selected)."

- Also as noted in the original post, RSYNC works fine from RN528 to RN424 as long as I choose a specific destination share ("RN212-Backup").  And - no authenticating is used (username/password are left blank). And - as posted earlier, I did try using authentication, made no difference. Finally, that "RN212-Backup" share has exactly the same settings as the Pictures share on the RN212, as far as I can tell from going through every settings screen. 

- And again, RN528-to-RN424 fails same as RN528-to-RN212 if I choose "Pictures" share as the destination folder (same as RN212). 

Seems like there's some kind of Permissions issue or other issue with trying to backup to the "Pictures" shares on either NAS.