why do delegates in acumatica get an c casting error when a view calls another method?

Change the reportVersions() method by this

    protected virtual IEnumerable reportVersions()
    {
        return GetVersions();
    }  

or

    protected virtual IEnumerable reportVersions()
    {
        foreach (var item in GetVersions())
        {
            yield return item;
        }
    }