Unable to copy actual files on remote using git-annex

Question

I currently want to deploy my existing git-annex repository on a new computer.

My configuration is the following one:

• on serverA: I have a git bare (with git-annex) repository and no actual files
• on serverB: I have an classical git-annex local folder which contains the actual (heavy) files (synced with serverA's repository)
• on serverC: I want to create a new git-annex repository and copy the files from serverB on it

Notice that I am not able to clone directly from serverBon serverC.

I follow the process:

• on serverC: git clone ssh://serverA/<path> after I run git annex init origin and git annex sync
• on serverB: git remote add NEW ssh://serverC/<path>, git annex sync NEW and it works. But when I want to copy the actual (heavy) files using git annex sync NEW --content, no file are copied and I have for each file the following error: copy <file> (unable to check NEW) failed.

Any idea of the raeson of these errors (notice that debug mode provide no additional information)?

Notice that all servers use version 8.xx of git-annex