Set one of the monitors to use 125% DPI scaling. Start the attached project on a monitor with 100% DPI scaling - the form is expected to be with size 400,400. Move the form to the monitor with 125% DPI scaling. You are expecting the form's size to be 500,500, but it is 507,521. Please refer to the screenshots.

Workaround:

Override the RadForm.ScaleControl method as follows:

    Protected Overrides Sub ScaleControl(factor As SizeF, specified As BoundsSpecified)
        Dim initialSize As Size = Me.Size
        MyBase.ScaleControl(factor, specified)
        Me.Size = TelerikDpiHelper.ScaleSize(initialSize, factor)
    End Sub