Client hanged at shutdown

This issue is marked as minor because it's been observed only once and we haven't been able to reproduce it since then.
The component using couchbase failed to shut down gracefully, and, after analyzing stacktrace, following two blocked couchbase threads were noticed - their stack traces follow:

First:

"New I/O worker #14" prio=10 tid=0x00007fcdfc159000 nid=0x409 waiting for monitor entry [0x00007fcddb6f5000]
java.lang.Thread.State: BLOCKED (on object monitor)
at com.couchbase.client.vbucket.ConfigurationProviderHTTP.getBucket(ConfigurationProviderHTTP.java:125)

• waiting to lock <0x0000000745f9d2a8> (a com.couchbase.client.vbucket.ConfigurationProviderHTTP)
  at com.couchbase.client.vbucket.BucketMonitor.notifyDisconnected(BucketMonitor.java:118)
  at com.couchbase.client.vbucket.BucketUpdateResponseHandler.handleUpstream(BucketUpdateResponseHandler.java:187)
  at org.jboss.netty.channel.DefaultChannelPipeline.sendUpstream(DefaultChannelPipeline.java:565)
  at org.jboss.netty.channel.DefaultChannelPipeline$DefaultChannelHandlerContext.sendUpstream(DefaultChannelPipeline.java:793)
  at org.jboss.netty.handler.codec.replay.ReplayingDecoder.cleanup(ReplayingDecoder.java:573)
  at org.jboss.netty.handler.codec.frame.FrameDecoder.channelDisconnected(FrameDecoder.java:366)
  at org.jboss.netty.channel.SimpleChannelUpstreamHandler.handleUpstream(SimpleChannelUpstreamHandler.java:107)
  at org.jboss.netty.channel.DefaultChannelPipeline.sendUpstream(DefaultChannelPipeline.java:565)
  at org.jboss.netty.channel.DefaultChannelPipeline.sendUpstream(DefaultChannelPipeline.java:560)
  at org.jboss.netty.channel.Channels.fireChannelDisconnected(Channels.java:399)
  at org.jboss.netty.channel.Channels$4.run(Channels.java:389)
  at org.jboss.netty.channel.socket.ChannelRunnableWrapper.run(ChannelRunnableWrapper.java:41)
  at org.jboss.netty.channel.socket.nio.AbstractNioWorker.processEventQueue(AbstractNioWorker.java:378)
  at org.jboss.netty.channel.socket.nio.AbstractNioWorker.run(AbstractNioWorker.java:259)
  at org.jboss.netty.channel.socket.nio.NioWorker.run(NioWorker.java:35)
  at org.jboss.netty.util.ThreadRenamingRunnable.run(ThreadRenamingRunnable.java:102)
  at org.jboss.netty.util.internal.DeadLockProofWorker$1.run(DeadLockProofWorker.java:42)
  at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)
  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)
  at java.lang.Thread.run(Thread.java:662) Locked ownable synchronizers: - <0x0000000745dca468> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)

Second:

"HttpConfigurationProvider Reloader" prio=10 tid=0x00007fcde406d800 nid=0x406 waiting on condition [0x00007fcddb8f7000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park(Native Method)

• parking to wait for <0x0000000745d30978> (a java.util.concurrent.CountDownLatch$Sync)
  at java.util.concurrent.locks.LockSupport.park(LockSupport.java:156)
  at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:811)
  at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedInterruptibly(AbstractQueuedSynchronizer.java:969)
  at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireSharedInterruptibly(AbstractQueuedSynchronizer.java:1281)
  at java.util.concurrent.CountDownLatch.await(CountDownLatch.java:207)
  at com.couchbase.client.vbucket.BucketUpdateResponseHandler.getReceivedFuture(BucketUpdateResponseHandler.java:149)
  at com.couchbase.client.vbucket.BucketUpdateResponseHandler.getLastResponse(BucketUpdateResponseHandler.java:129)
  at com.couchbase.client.vbucket.BucketMonitor.startMonitor(BucketMonitor.java:219)
  at com.couchbase.client.vbucket.ConfigurationProviderHTTP.subscribe(ConfigurationProviderHTTP.java:339)
• locked <0x0000000745f9d2a8> (a com.couchbase.client.vbucket.ConfigurationProviderHTTP)
  at com.couchbase.client.vbucket.provider.BucketConfigurationProvider.monitorBucket(BucketConfigurationProvider.java:361)
  at com.couchbase.client.vbucket.provider.BucketConfigurationProvider.access$900(BucketConfigurationProvider.java:65)
  at com.couchbase.client.vbucket.provider.BucketConfigurationProvider$HttpProviderRefresher.run(BucketConfigurationProvider.java:610)
  at java.lang.Thread.run(Thread.java:662) Locked ownable synchronizers: - None

Hope some light can be shed on this strange behavior.
Thank you very much in advance!