Upgraded to 6.1.7 from 6.1.4 issues migrating multi-domain Authentication code

Authenticator.Instance.LoginAsync(
credentials,
new LoginOptions(credentials.Domain),
loginOperation =>
{
    if (loginOperation.CompletedSuccessfully
        && loginOperation.AuthenticationContext.LoginState == LoginState.LoggedIn)
    {
        Authenticator.Instance.DefaultAuthenticationContext = loginOperation.AuthenticationContext;
        this.OnLoginSuccessfull();
    }
    else if (loginOperation.HasError)
    {
        loginOperation.MarkErrorAsHandled();
        this.OnLoginError(loginOperation.Error, true);
    }
});

var manager = new MyManager(true, credentials.Domain)

var context = Authenticator.Instance.Login(credentials, new LoginOptions(accountId));
var applicationManager = new MyApplicationEntities(entityManager, true, accountId);

var credentials = new FormsAuthenticationLoginCredential(userName, password, accountId, false);
var context = Authenticator.Instance.Login(credentials);

public class LoginManager : IEntityLoginManager
    {
        private EntityManager entityManager;
        public LoginManager()
        {
        }
        [Import]
        public IMembershipService MembershipService { get; set; }
        public IPrincipal Login(ILoginCredential credential, EntityManager manager)
        {
            this.entityManager = manager;
            if (credential == null) throw new LoginException(LoginExceptionType.NoCredentials, "Credentials required");
            return this.CredentialAuthentication(credential);
        }
        public void Logout(IPrincipal principal, EntityManager manager)
        {
            FormsAuthentication.SignOut();
        }
        private IPrincipal CredentialAuthentication(ILoginCredential credential)
        {
            var isAuthenticated = this.MembershipService.ValidateUser(this.entityManager, credential.Domain, credential.UserName, credential.Password);
...
        }
    }

public bool ValidateUser(EntityManager entityManager, string accountId, string userName, string password)
{
    var passwordFromDatabase = string.Empty;
    var passwordSalt = string.Empty;
    int? failedPasswordAttemptCount = 0;
    int? failedSecurityAnswerAttemptCount = 0;
    bool? isActive = false;
    DateTime? lastActivityDate = DateTime.Now;
    int? retVal = 0;
    try
    {
        var applicationManager = new MyApplicationEntities(entityManager, true, accountId);
        applicationManager.MEMGetUserPassword(
            userName,
            true,
            ref passwordFromDatabase,
            ref passwordSalt,
            ref failedPasswordAttemptCount,
            ref failedSecurityAnswerAttemptCount,
            ref isActive,
            ref lastActivityDate,
            ref retVal);
        var encodedPasswd = EncodeWithSalt(password, passwordSalt);
        var isPasswordCorrect = passwordFromDatabase.Equals(encodedPasswd);
        if (isPasswordCorrect && failedPasswordAttemptCount == 0 && failedSecurityAnswerAttemptCount == 0)
        {
            return true;
        }
        return isPasswordCorrect;
    }
    catch (Exception ex)
    {
        this.LoggerService.Log(accountId, ex, Category.Exception, Priority.Medium);
        return false;
    }
}

var applicationManager = new MyApplicationEntities(entityManager, true, accountId);