I'm using Vorto in combination with the ModelsBuilder and have a property wich is a multi url picker, but it won't return a list of UrlPickers.

I've another property for Vorto that uses a single URL Picker and it returns a UrlPicker Model correctly.

Both items are filled in Umbraco.

What's the difference between these and how can I fix it?

Single URL picker code in Partial Class (the override of the default class):

///<summary>
    ///Category column 3
    ///</summary>
    [ImplementPropertyType("footerColumn3Category")]
    public UrlPicker.Umbraco.Models.UrlPicker FooterColumn3Category
    {
        get { return this.GetVortoValue<UrlPicker.Umbraco.Models.UrlPicker>("footerColumn3Category", fallbackCultureName: "en-US"); }
    }

Multi URL picker code in Partial Class (the override of the default class):

///<summary>
    ///Items column 3
    ///</summary>
    [ImplementPropertyType("footerColumn3Items")]
    public IEnumerable<UrlPicker.Umbraco.Models.UrlPicker> FooterColumn3Items
    {
        get { return this.GetVortoValue<IEnumerable<UrlPicker.Umbraco.Models.UrlPicker>>("footerColumn3Items", fallbackCultureName: "en-US"); }
    }