The first message sent has the destination field initialized with null. In result, the first message is broadcasted. The destination must be set.

In here: https://github.com/belaban/JGroups/blob/master/src/org/jgroups/blocks/RequestCorrelator.java#L161

Code:
Message copy=(first? msg : msg.copy(true)).dest(mbr);

Possible fix:
Message copy=(first? msg.dest(mbr) : msg.copy(true)).dest(mbr);