Poor support for custom DPI scaling in Windows 7 - Windows 10.
There no null checking, and there is dirty hacks:

CASE 1: RadPageViewElement
 public override void DpiScaleChanged(SizeF scaleFactor)
        {
            base.DpiScaleChanged(scaleFactor);

            if (this.Owner != null && this.Owner.Pages.Count > 1)
            {
                this.Owner.SuspendEvents();

                if (this.Owner.SelectedPage == this.Owner.Pages[0])
                {
                    this.Owner.SelectedPage = this.Owner.Pages[1]; // NO NULL CHECKING
                    this.Owner.SelectedPage = this.Owner.Pages[0]; // DIRTY HACK: users can have their own processing OnSelectedPage, which is unexpected here!
                }
                else
                {
                    RadPageViewPage page = this.Owner.SelectedPage;
                    this.Owner.SelectedPage = this.Owner.Pages[0];
                    this.Owner.SelectedPage = page;
                }

CASE 2:
 public partial class RadForm1 : Telerik.WinControls.UI.RadForm
    {
        public RadForm1()
        {
            InitializeComponent();
            radWizard1.Pages.Add(new WizardPage()); // when user has 100% Dpi, this code works normally. But if user has custom scale DPI (e.g. 101%), user received System.NullReferenceException: 'Object reference not set to an instance of an object.' (because because again there is no verification for ContentArea = null)...
        }
    }

Please improve the work with custom DPI scaling!