Error 503 GhostCode 19922 Ghosting to Drobo Network Drive

Where I work we are having problems ghosting to a Drobo B800FS network drive. It was working when the drive was empty but when it got to over 50% used space we started getting timeout errors. We moved the console to a new PC, it is on a Gigabit network and I added -SLOWFILE and -BUFFERSIZE=32 to the image creation tasks. This seemed to help a little but we are still getting Error 503, Connection timed out with GhostCode 19922 or 19945 on some PCs. Also, when the image creation tasks goes off it says Unicast and not mulitcast. Under options it is set to multicast, does this mean multicasting it not enabled on the network? I'm not sure if this is related to our problem or not, we are trying to narrow it down.

Thanks