It sounds like your cluster contains members using different JGroups versions. This does not work. Your WF 10.1 nodes and WF 10.0 nodes should be isolated. e.g. by using distinct MPING multicast address/ports.
Thanks for the reply, Paul, that makes sense. I have two follow-up questions:
1. Shouldn't Version#isBinaryCompatible guard against this?
2. Does changing the channel name work for isolating the old nodes from the new ones?