Backup's producing 0 byte length files

Hi,
All our FreePBX Servers are version 5.211.65-12. All are kept up to date with module admin. Since June 1/14 the backups no longer are sent to the FTP server. Running the backup manually with the ‘and-run’ button produces a 0 byte length filename.tgz

The configuration for the ftp backup is active. To be sure there was no problem on the backup server, as root ftp’d one backup file as shown below without any issue:

ftp> put 20140603-104428-1401806668-2080148570.tgz
local: 20140603-104428-1401806668-2080148570.tgz remote: 20140603-104428-1401806668-2080148570.tgz
200 PORT command successful
150 Opening BINARY mode data connection for 20140603-104428-1401806668-2080148570.tgz
226 Transfer complete
147297377 bytes sent in 56.2 secs (2620.08 Kbytes/sec)

md5sum On FreePBX server:
9ca95ee474eb1d32e65a9b0a48909a8f 20140603-104428-1401806668-2080148570.tgz

md5sum on backup server:
MD5 (20140603-104428-1401806668-2080148570.tgz) = 9ca95ee474eb1d32e65a9b0a48909a8f

What has changed in FreePBX to cause 0 byte length backups and what must be done to get this working properly again?

Thanks.