如何诊断/修复此NHibernate.PropertyAccessException？

给出以下Fluent NHibernate地图：

public class FastTrackPackageClassMap : ClassMap<FastTrackPackage>
{
    public FastTrackPackageClassMap()
    {
        Id(x => x.Id);
        References(x => x.UserCreated, "UserIdCreated").Cascade.None();
        References(x => x.UserSent, "UserIdSent").Nullable().Cascade.None();
        HasMany(x => x.GetFileHeaders()).KeyColumn("PackageId").ForeignKeyConstraintName("PackageId").Cascade.AllDeleteOrphan().Not.LazyLoad().Inverse();
        HasMany(x => x.GetEmailRecords()).KeyColumn("PackageId").ForeignKeyConstraintName("PackageId").Cascade.AllDeleteOrphan().Not.LazyLoad().Inverse();
        HasMany(x => x.GetPaymentRecords()).KeyColumn("PackageId").ForeignKeyConstraintName("PackageId").Cascade.AllDeleteOrphan().Not.LazyLoad().Inverse();
        HasMany(x => x.GetFileTrailers()).KeyColumn("PackageId").ForeignKeyConstraintName("PackageId").Cascade.AllDeleteOrphan().Not.LazyLoad().Inverse();
        Map(x => x.TestPackage);
        Map(x => x.DateTimeCreated).Generated.Insert();
        Map(x => x.DateTimeSent).Nullable();
    }
}

public class FileHeaderFastTrackRecordClassMap : ClassMap<FileHeaderFastTrackRecord>
{
    public FileHeaderFastTrackRecordClassMap()
    {
        Id(FileHeaderFastTrackRecord.Expressions.Id);
        References(x => x.Package, "PackageId");
        Map(x => x.FileDateTime);
        Map(x => x.CustomerId);
        Map(x => x.TestPackage, "TestIndicator").CustomType(typeof (TestPackageUserType));
        Map(x => x.BankId);
    }
}

当我将FastTrackPackage与子文件HeaderFastTrackRecord合并时，我收到以下异常并进行堆栈：

NHibernate.PropertyAccessException: Invalid Cast (check your mapping for property type mismatches); setter of BNYM_Extranet.Common.RemEDIFastTrack.FileHeaderFastTrackRecord

at NHibernate.Tuple.Entity.PocoEntityTuplizer.SetPropertyValuesWithOptimizer(Object entity, Object[] values)
at NHibernate.Tuple.Entity.PocoEntityTuplizer.SetPropertyValues(Object entity, Object[] values)
at NHibernate.Persister.Entity.AbstractEntityPersister.SetPropertyValues(Object obj, Object[] values, EntityMode entityMode)
at NHibernate.Event.Default.DefaultMergeEventListener.CopyValues(IEntityPersister persister, Object entity, Object target, ISessionImplementor source, IDictionary copyCache)
at NHibernate.Event.Default.DefaultMergeEventListener.EntityIsDetached(MergeEvent event, IDictionary copyCache)
at NHibernate.Event.Default.DefaultMergeEventListener.OnMerge(MergeEvent event, IDictionary copyCache)
at NHibernate.Impl.SessionImpl.FireMerge(IDictionary copiedAlready, MergeEvent event)
at NHibernate.Impl.SessionImpl.Merge(String entityName, Object obj, IDictionary copiedAlready)
at NHibernate.Engine.CascadingAction.MergeCascadingAction.Cascade(IEventSource session, Object child, String entityName, Object anything, Boolean isCascadeDeleteEnabled)
at NHibernate.Engine.Cascade.CascadeToOne(Object child, IType type, CascadeStyle style, Object anything, Boolean isCascadeDeleteEnabled)
at NHibernate.Engine.Cascade.CascadeAssociation(Object child, IType type, CascadeStyle style, Object anything, Boolean isCascadeDeleteEnabled)
at NHibernate.Engine.Cascade.CascadeProperty(Object child, IType type, CascadeStyle style, Object anything, Boolean isCascadeDeleteEnabled)
at NHibernate.Engine.Cascade.CascadeCollectionElements(Object child, CollectionType collectionType, CascadeStyle style, IType elemType, Object anything, Boolean isCascadeDeleteEnabled)
at NHibernate.Engine.Cascade.CascadeCollection(Object child, CascadeStyle style, Object anything, CollectionType type)
at NHibernate.Engine.Cascade.CascadeAssociation(Object child, IType type, CascadeStyle style, Object anything, Boolean isCascadeDeleteEnabled)
at NHibernate.Engine.Cascade.CascadeProperty(Object child, IType type, CascadeStyle style, Object anything, Boolean isCascadeDeleteEnabled)
at NHibernate.Engine.Cascade.CascadeOn(IEntityPersister persister, Object parent, Object anything)
at NHibernate.Event.Default.DefaultMergeEventListener.CascadeOnMerge(IEventSource source, IEntityPersister persister, Object entity, IDictionary copyCache)
at NHibernate.Event.Default.DefaultMergeEventListener.EntityIsDetached(MergeEvent event, IDictionary copyCache)
at NHibernate.Event.Default.DefaultMergeEventListener.OnMerge(MergeEvent event, IDictionary copyCache)
at NHibernate.Event.Default.DefaultMergeEventListener.OnMerge(MergeEvent event)
at NHibernate.Impl.SessionImpl.FireMerge(MergeEvent event)
at NHibernate.Impl.SessionImpl.Merge(String entityName, Object obj)
at NHibernate.Impl.SessionImpl.Merge(Object obj)
at DAL.NHibernate.RepositoryWithTypedId`2.Update(T entity) in Repository.cs: line 72
at UnitTests.DAL.NHibernate.RemEDIFastTrack.FastTrackPackageRepositoryFixture.Update() in FastTrackPackageRepositoryFixture.cs: line 290 

当我

保存带有FileHeaderFastTrackRecord的FastTrackPackage时，我没有收到任何错误，它会正确保存。我还可以独立地
保存
和
更新
文件头FastTrackRecords

在这一点上，我不知所措。我怀疑自定义用户类型，但我不能确定

如何诊断或修复此问题？
结果表明“TestPackageUserType.Replace（）”方法是错误的。当它应该返回bool时，它返回了一个char，而代码被它阻塞了（提供了神秘的异常消息）。我的新
Replace（）
方法如下所示：

public object Replace(object original, object target, object owner)
{
  return original;
}

public object Replace(object original, object target, object owner)
{
  return original;
}