I'm seeing a NPE when Memcached server shutdowns:

Exception in thread "Thread-2" java.lang.RuntimeException: Exception encountered in shutting down the server
at org.infinispan.server.core.ShutdownHook.run(Main.scala:239)
Caused by: java.util.concurrent.ExecutionException: org.infinispan.CacheException: Unable to invoke method private void org.infinispan.transaction.xa.TransactionTable.stop() on object
at java.util.concurrent.FutureTask$Sync.innerGet(FutureTask.java:222)
at java.util.concurrent.FutureTask.get(FutureTask.java:83)
at org.infinispan.server.core.ShutdownHook.run(Main.scala:235)
Caused by: org.infinispan.CacheException: Unable to invoke method private void org.infinispan.transaction.xa.TransactionTable.stop() on object
at org.infinispan.util.ReflectionUtil.invokeAccessibly(ReflectionUtil.java:173)
at org.infinispan.factories.AbstractComponentRegistry$PrioritizedMethod.invoke(AbstractComponentRegistry.java:861)
at org.infinispan.factories.AbstractComponentRegistry.internalStop(AbstractComponentRegistry.java:709)
at org.infinispan.factories.AbstractComponentRegistry.stop(AbstractComponentRegistry.java:603)
at org.infinispan.factories.ComponentRegistry.stop(ComponentRegistry.java:166)
at org.infinispan.CacheDelegate.stop(CacheDelegate.java:325)
at org.infinispan.manager.DefaultCacheManager.stop(DefaultCacheManager.java:521)
at org.infinispan.server.core.ShutdownHook$$anon$5.call(Main.scala:230)
at org.infinispan.server.core.ShutdownHook$$anon$5.call(Main.scala:226)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
at java.util.concurrent.FutureTask.run(FutureTask.java:138)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:680)
Caused by: java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.infinispan.util.ReflectionUtil.invokeAccessibly(ReflectionUtil.java:170)
... 13 more
Caused by: java.lang.NullPointerException
at org.infinispan.manager.DefaultCacheManager.removeListener(DefaultCacheManager.java:541)
at org.infinispan.transaction.xa.TransactionTable.stop(TransactionTable.java:87)
... 18 more

The origin seems to be in ISPN-771

Maybe since transaction table now removes the listener, it needs to stop before the cache manager notifier does?