ServiceStack Ormlite Object column is not populated

Using ServiceStack Ormlite 5.12.0. I have a model looks like the following, saving the object is perfectly fine.

public string DescriptionAlias { get; set; }
    /// <summary>
    /// Applying PLUs (Price Lookup Code)
    /// Default is all
    /// </summary>
    [CustomField("LONGTEXT")]
    public Applying<string> ApplyingPlus { get; set; }
    /// <summary>
    /// Applying User Tags
    /// Default is all
    /// </summary>
    [CustomField("LONGTEXT")]
    public Applying<string> ApplyingUserTags { get; set; }
    /// <summary>
    /// Applying User Groups
    /// Default is all
    /// </summary>
    [CustomField("LONGTEXT")]
    public Applying<int> ApplyingUserGroups { get; set; }

When LoadSelect or Select the object, all Complex object Applying Columns are not populated.