B800fs refused by target

I have two B800fs’ at work, one is the Main storage drive (A) and the other a back up(B). I set up Drobo Sync between A & B within the SAN and successfully backed up A to B

now I want to move B onto another floor within the building, when I plug it in Drobo dashboard finds B however when I go to sync it initialises and after about 10min will produce the error message “Failed (connection refused by target)”

I then moved B back into the same room as A and Drobo Sync works perfectly.

We have other NAS servers within the building so bandwidth isn’t the bottleneck and both Drobos are within the Same area network. I’m stumped.

anybody had the same issue and fixed it ??