WebLogic: all MS in a cluster hang while starting up.... weblogic.cluster.MemberManager.getJNDIStateDump issue

in the thread dump of both MS I see several blocked threads:

weblogic.cluster.MemberManager.getRemoteMembers
weblogic.iiop.ClusterServices.getMembers
weblogic.cluster.ClusterRuntime.clusterMembersChanged
weblogic.cluster.MemberManager.findOrCreate
plus some 150 DynamicJSSEListenThread threads....
In particular all BLOCKED threads are waiting for lock 0x000000060276f168 who is held by this getJNDIStateDump:

"[STANDBY] ExecuteThread: '2' for queue: 'weblogic.kernel.Default (self-tuning)'" daemon prio=10 tid=0x00007f6a800024c0 nid=0x74bd runnable [0x00007f6b1f7e6000]
   java.lang.Thread.State: RUNNABLE
               at java.net.SocketInputStream.socketRead0(Native Method)
               at java.net.SocketInputStream.read(SocketInputStream.java:152)
               at java.net.SocketInputStream.read(SocketInputStream.java:122)
               at sun.security.ssl.InputRecord.readFully(InputRecord.java:442)
               at sun.security.ssl.InputRecord.read(InputRecord.java:480)
               at sun.security.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:946)
               - locked <0x000000060bcf5160> (a java.lang.Object)
               at sun.security.ssl.SSLSocketImpl.readDataRecord(SSLSocketImpl.java:903)
               at sun.security.ssl.AppInputStream.read(AppInputStream.java:102)
               - locked <0x000000060bd2a9b0> (a sun.security.ssl.AppInputStream)
               at java.io.BufferedInputStream.fill(BufferedInputStream.java:235)
               at java.io.BufferedInputStream.read1(BufferedInputStream.java:275)
               at java.io.BufferedInputStream.read(BufferedInputStream.java:334)
               - locked <0x000000060bd2a988> (a java.io.BufferedInputStream)
               at sun.net.www.http.HttpClient.parseHTTPHeader(HttpClient.java:690)
               at sun.net.www.http.HttpClient.parseHTTP(HttpClient.java:633)
               at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1325)
               - locked <0x000000060c29d3c8> (a sun.net.www.protocol.https.DelegateHttpsURLConnection)
               at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:254)
               - locked <0x000000060c29d4a8> (a sun.net.www.protocol.https.HttpsURLConnectionImpl)
               at weblogic.cluster.MemberManager.getJNDIStateDump(MemberManager.java:244)
               at weblogic.cluster.MemberManager.waitForSync(MemberManager.java:222)
               at weblogic.cluster.MemberManager.waitToSyncWithCurrentMembers(MemberManager.java:182)
               - locked <0x000000060276f168> (a weblogic.cluster.MemberManager)
               at weblogic.cluster.InboundService.start(InboundService.java:52)
               at weblogic.server.AbstractServerService.postConstruct(AbstractServerService.java:78)
               at sun.reflect.GeneratedMethodAccessor6.invoke(Unknown Source)
               at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
               at java.lang.reflect.Method.invoke(Method.java:606)
               at org.glassfish.hk2.utilities.reflection.ReflectionHelper.invoke(ReflectionHelper.java:1017)
               at org.jvnet.hk2.internal.ClazzCreator.postConstructMe(ClazzCreator.java:388)
               at org.jvnet.hk2.internal.ClazzCreator.create(ClazzCreator.java:430)
               at org.jvnet.hk2.internal.SystemDescriptor.create(SystemDescriptor.java:456)
               at org.glassfish.hk2.runlevel.internal.AsyncRunLevelContext.findOrCreate(AsyncRunLevelContext.java:225)
               at org.glassfish.hk2.runlevel.RunLevelContext.findOrCreate(RunLevelContext.java:82)
               at org.jvnet.hk2.internal.Utilities.createService(Utilities.java:2488)
               at org.jvnet.hk2.internal.ServiceHandleImpl.getService(ServiceHandleImpl.java:98)
               - locked <0x000000060acd0028> (a java.lang.Object)
               at org.jvnet.hk2.internal.ServiceHandleImpl.getService(ServiceHandleImpl.java:87)
               at org.glassfish.hk2.runlevel.internal.CurrentTaskFuture$QueueRunner.oneJob(CurrentTaskFuture.java:1162)
               at org.glassfish.hk2.runlevel.internal.CurrentTaskFuture$QueueRunner.run(CurrentTaskFuture.java:1147)
               at weblogic.work.SelfTuningWorkManagerImpl$WorkAdapterImpl.run(SelfTuningWorkManagerImpl.java:553)
               at weblogic.work.ExecuteThread.execute(ExecuteThread.java:311)
               at weblogic.work.ExecuteThread.run(ExecuteThread.java:263)

It turned out that the SAME domain was running before on a different set of servers, and while migrating them the operator forgot to shut down the previous instances. How this could interfere with the current domain, it's still a mystery