See attached source.
When executing G2 + G1 using tunnel.xml configuration
G1 produces the following error:

failure in TUNNEL receiver thread
java.lang.RuntimeException: class for magic number 32256 not found
at org.jgroups.util.Util.readOtherAddress(Util.java:914)
at org.jgroups.util.Util.readAddress(Util.java:885)
at org.jgroups.util.Util.readAddresses(Util.java:963)
at org.jgroups.stack.GossipData.readFrom(GossipData.java:124)
at org.jgroups.protocols.TUNNEL$StubReceiver.run(TUNNEL.java:340)
at java.lang.Thread.run(Thread.java:619)

This problem does not occur when using default configuration (udp.xml)
It also does not occur if the getList returns an empty list.