AD Sync Get Changes: Collection was modified

Via email with Bob Bradley:

Operation bccdc996-f23b-46a0-87ad-607a093ce096 failed in
operation list with id add13e6e-e8b3-4336-b9aa-b9c62943a855 for the following
reason. This is retry number 0: Unify.Framework.UnifyEngineException: Error in
stored values engine attempting to write to storage, see the inner exception.
---> System.InvalidOperationException: Collection was modified; enumeration
operation may not execute.
   at System.Collections.Generic.Dictionary`2.Enumerator.MoveNext()
   at WriteArrayOfKeyValueOfGroupedNameValueCollectionKeyanyType70DdoCVIToXml(XmlWriterDelegator, Object , XmlObjectSerializerWriteContext , CollectionDataContract )
   at System.Runtime.Serialization.CollectionDataContract.WriteXmlValue(XmlWriterDelegator xmlWriter, Object obj, XmlObjectSerializerWriteContext context)
   at System.Runtime.Serialization.XmlObjectSerializerWriteContext.SerializeAndVerifyType(DataContract dataContract, XmlWriterDelegator xmlWriter, Object obj, Boolean verifyKnownType, RuntimeTypeHandle declaredTypeHandle, Type declaredType)
   at System.Runtime.Serialization.XmlObjectSerializerWriteContext.SerializeWithXsiType(XmlWriterDelegator xmlWriter, Object obj, RuntimeTypeHandle objectTypeHandle, Type objectType, Int32 declaredTypeID, RuntimeTypeHandle declaredTypeHandle, Type declaredType)
   at System.Runtime.Serialization.XmlObjectSerializerWriteContext.InternalSerialize(XmlWriterDelegator xmlWriter, Object obj, Boolean isDeclaredType, Boolean writeXsiType, Int32 declaredTypeID, RuntimeTypeHandle declaredTypeHandle)
   at System.Runtime.Serialization.XmlObjectSerializerWriteContext.InternalSerializeReference(XmlWriterDelegator xmlWriter, Object obj, Boolean isDeclaredType, Boolean writeXsiType, Int32 declaredTypeID, RuntimeTypeHandle declaredTypeHandle)
   at WriteStoredValueCollectionToXml(XmlWriterDelegator , Object , XmlObjectSerializerWriteContext , ClassDataContract )
   at System.Runtime.Serialization.ClassDataContract.WriteXmlValue(XmlWriterDelegator xmlWriter, Object obj, XmlObjectSerializerWriteContext context)
   at System.Runtime.Serialization.DataContractSerializer.InternalWriteObjectContent(XmlWriterDelegator writer, Object graph, DataContractResolver dataContractResolver)
   at System.Runtime.Serialization.DataContractSerializer.InternalWriteObject(XmlWriterDelegator writer, Object graph, DataContractResolver dataContractResolver)
   at System.Runtime.Serialization.XmlObjectSerializer.WriteObjectHandleExceptions(XmlWriterDelegator writer, Object graph, DataContractResolver dataContractResolver)
   at System.Runtime.Serialization.XmlObjectSerializer.WriteObject(XmlDictionaryWriter writer, Object graph)
   at System.Runtime.Serialization.XmlObjectSerializer.WriteObject(Stream stream, Object graph)
   at Unify.Framework.StoredValues.IsolatedStoredValuesEngineBase.<>c__DisplayClass14_0.<SaveStoredValuesCollection>b__0()
   at Unify.Framework.ExtensionMethods.WaitOnMutex(Mutex mutex, Action work)
   at Unify.Framework.StoredValues.IsolatedStoredValuesEngineBase.SaveStoredValuesCollection(IStoredValueCollection storedValueCollection)
   --- End of inner exception stack trace ---
   at Unify.Framework.StoredValues.IsolatedStoredValuesEngineBase.SaveStoredValuesCollection(IStoredValueCollection storedValueCollection)
   at Unify.Product.EventBroker.ADSyncChangesPlugIn.GetChanges(DirectorySearcher searcher)
   at Unify.Product.EventBroker.ADChangesPlugInBase.Check()
   at Unify.Product.EventBroker.OperationListExecutorBase.RunCheck(ICheckOperationFactoryInformation checkOperation)<span></span>