Windows includes a number of folders that are actually links to other folders. In some cases they are recursive links, i.e. they link back to one of their own parent folders. This effectively means the folder contains an infinite number of child folders. SyncBack can detect these infinite loops of folders. When it detects them a warning is recorded in the log file that states which folder (and where the folder points to).
For example, the \Users\[username]\AppData\Local\Application Data\ folder links back to \Users\[username]\AppData\Local\
You can safely ignore these warnings if they refer to the \Users\ folder.
To avoid these issues:
- Modify your profile
- Switch to Expert mode
- Go to the Copy/Delete -> Links tab
- Enable either Ignore NTFS junction points or Ignore Windows backwards compatibility junction points
Note that the recursive warning can also be given if a folder has already been copied, e.g. as it is linked to via another junction point, i.e. it is not necessarily recursive it could be that a folder is linked to more than once.
For more information on junction/mount points see this article:
https://help.2brightsparks.com/support/solutions/articles/43000335955
Also, you can refer to this article:
https://www.2brightsparks.com/resources/articles/ntfs-hard-links-junctions-and-symbolic-links.html