At EJBRemoteTransactionPropagatingInterceptor, a transaction that has been already open at current server could be ignored, thus causing the transaction to be reimported, resulting in the double diamond problem. To reproduce you need a reinvocation at a server that was already participating in the transaction, as the scenario below for example: server1 -> server2 -> server1
Closing as this was fixed in EAP 6.4 CP13, so this is a duplicate of another one possibly: https://bugzilla.redhat.com/show_bug.cgi?id=1378396