Run the attached sample project and select the second page. You will notice that the tasks are missing. This used to work in R2 2019 (version 2019.2.508).

Workaround: Initialize the RadGanttView.BindingContext before adding it to the page:

        Dim Gantt As New RadGanttView
        Gantt.Dock = DockStyle.Fill
        Gantt.BindingContext = New BindingContext()
        RadPageViewPage2.Controls.Add(Gantt)