'DocEntity+MlInterfaces.Owner' field, which is declared as paired to 'DocEntity.Interfaces' field, should be of type 'DocEntity' but actually it is 'DocEntity'. This is how everything is defined:

[HierarchyRoot(InheritanceSchema = InheritanceSchema.ConcreteTable)]
    [Id("F3F91774-1F7F-41EF-0000-000000000000")]
    [Serializable]
    public abstract class Multilink<TOwner, TLinked> : EntityBase, IMultilink, IOwned
        where TOwner : EntityBase
        where TLinked : EntityBase
    {
        protected Multilink(Guid id, TOwner owner) : base(id)
        {
            Owner = owner;
        }

        /// <summary>
        /// Зависимый
        /// Элемент на который ссылается мультилинк
        /// </summary>
        [Field(Nullable = false)]
        [Association(OnOwnerRemove = OnRemoveAction.Clear, OnTargetRemove = OnRemoveAction.Deny)]
        [Id("00000000-0000-0000-8326-53CB24F7B5D8")]
        public TLinked Linked { get; set; }

        /// <summary>
        /// Владелец
        /// Элемент содержащий мультилинк
        /// </summary>
        [Field(Nullable = false)]
        [Association(OnOwnerRemove = OnRemoveAction.Clear, OnTargetRemove = OnRemoveAction.Cascade)]
        [Id("00000000-0000-0000-B50D-27F9E2E3DB9F")]
        public TOwner Owner { get; set; }
    }

public partial class DocEntity
    {
        /// <summary>
        /// Мультилинк сущности и интерфейсов
        /// </summary>
        /// <revision>$Rev$</revision>        
        [Id("629409A9-C9E4-47D2-0000-000000000000")]
        public partial class MlInterfaces : Multilink<DocEntity, EnEntityInterface>
        {
            public MlInterfaces(Guid id, DocEntity owner)
                : base(id, owner)
            {
            }
        }
    }

[Id("C859E9F9-8196-42CE-0000-000000000000")]
    [Index("SysName", Unique = true, Name = "DocEntity.IX_SysName")]
    public partial class DocEntity : Werp.Model.Models.Base.DocumentBase, IRevisioned, IHierarchical<DocEntity>
    {
        [Association(PairTo = "Owner", OnTargetRemove = OnRemoveAction.Clear, OnOwnerRemove = OnRemoveAction.Cascade)]
        [Field]
        [Id("00000000-0000-0000-8235-49FE5D2F482A")]
        public EntitySet<DocEntity.MlInterfaces> Interfaces { get; set; }
}