EntityFramework only updates my foreign key once after app boot

            kernel.Bind<DbContext>().
                ToSelf().
                InSingletonScope().
                WithConstructorArgument("nameOrConnectionString", connectionString);

        public void Update(E entity)
        {
            dbCommonContext.Entry<E>(entity).State = EntityState.Modified;
            dbCommonContext.SaveChanges();

        }

        public void SetDefaultCreditCard(int userId, int creditCardId)
        {
            var creditCard = CreditCardDao.Find(creditCardId);
            if (creditCard.userId != userId)
            {
                throw new PermissionDeniedException("Solo puedes asignar una tarjeta por defecto si es tuya.");
            }

            var appUser = AppUserDao.Find(userId);
            appUser.defaultCardId = creditCardId;
            appUser.CreditCard = creditCard;
            AppUserDao.Update(appUser);
        }

            var userSession = SessionManager.GetUserSession(Context);
            var iocManager = (IIoCManager)Context.Application["managerIoC"];
            var userService = iocManager.Resolve<IUserService>();
                    userService.SetDefaultCreditCard((int)userSession.UserId, cardId);