The error message is correct for the wrong reason, and it should have no bearing on your problem. The 239.x range is part of multi-cast - generally non-routed traffic.
NetRange: 224.0.0.0 - 239.255.255.255
CIDR: 224.0.0.0/4
NetName: MCAST-NET
NetHandle: NET-224-0-0-0-1
Parent:
NetType: IANA Special Use
Comment: This block is reserved for special purposes.
Comment: Please see RFC 3171 for additional information.
RegDate: 1991-05-22
Updated: 2002-09-16
The first thing to do when a scripted process isn't working right for any system is to manually do the script yourself and watch for errors that may be failing the script but not preventing it from working.
Also you are a not very clear on when in the script the compression happens. It is possible to setup a FTP Server such that if a flat file is requested with a compressed extension (.gz or gzip in this case) that the file is compressed and then sent. This is something that the remote FTP server has to support, your local system has no effect except for how the file is requested in your script.
You also imply though you don't state that each of the systems being backed up have their own scripts. If that is the case, compare the scripts for two similar systems and see what is different. one of those two should show you the problem plainly.
