To reproduce: 

1. Add a RadScheduler, a RadSchedulerNavigator and a RadButton. Use the following code and run the project:

private void radButton1_Click(object sender, EventArgs e)
{
    SchedulerTimelineView timelineView = radScheduler1.GetTimelineView(); 
    this.radScheduler1.FocusedDate = new DateTime(DateTime.Now.Year,DateTime.Now.Month,1);
    timelineView.ShowTimescale(Timescales.Weeks);
    this.radScheduler1.SchedulerElement.UpdateCellContainers();
}

2. Switch to Timeline view and change the scaling to Hour.
3. Add and appointment and click the button. You will notice that the appointment is missing.

Workaround: change the FocusedDate after the scaling is changed.