ConcurrentException in update of RemoteAuxiliaryCache

We have the same application that runs on two distinct node.  This application is basically a rest statefull service that uses a Remote JCS cache in order to share sessions, but frequently we got the following excpetion:

ERROR RemoteCache:141 - Disabling remote cache due to error: Failed to put [fe3e6602-d2bb-497d-b2bc-3a809d9b0d3f] to
navigationdata
java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextNode(HashMap.java:1442)
at java.util.HashMap$KeyIterator.next(HashMap.java:1466)
at java.util.HashSet.writeObject(HashSet.java:287)
at sun.reflect.GeneratedMethodAccessor173.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:1140)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1496)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)
at java.util.HashMap.internalWriteEntries(HashMap.java:1790)
at java.util.HashMap.writeObject(HashMap.java:1363)
at sun.reflect.GeneratedMethodAccessor175.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:1140)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1496)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)

at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)
at java.util.ArrayList.writeObject(ArrayList.java:766)
at sun.reflect.GeneratedMethodAccessor172.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:1140)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1496)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)
at org.apache.commons.jcs.utils.serialization.StandardSerializer.serialize(StandardSerializer.java:55)
at org.apache.commons.jcs.utils.serialization.SerializationConversionUtil.getSerializedCacheElement(SerializationConversionUtil.java:74)
at org.apache.commons.jcs.auxiliary.remote.AbstractRemoteAuxiliaryCache.processUpdate(AbstractRemoteAuxiliaryCache.java:421)
at org.apache.commons.jcs.auxiliary.AbstractAuxiliaryCacheEventLogging.updateWithEventLogging(AbstractAuxiliaryCacheEventLogging.java:65)
at org.apache.commons.jcs.auxiliary.AbstractAuxiliaryCacheEventLogging.update(AbstractAuxiliaryCacheEventLogging.java:50)
at org.apache.commons.jcs.engine.CacheAdaptor.handlePut(CacheAdaptor.java:96)
at org.apache.commons.jcs.engine.AbstractCacheEventQueue$PutEvent.doRun(AbstractCacheEventQueue.java:362)
at org.apache.commons.jcs.engine.AbstractCacheEventQueue$AbstractCacheEvent.run(AbstractCacheEventQueue.java:281)
at org.apache.commons.jcs.engine.CacheEventQueue$QProcessor.run(CacheEventQueue.java:228)