To reproduce: use the following code:

public Form1()
{
    InitializeComponent();
    
    Appointment recurringAppointment = new Appointment(DateTime.Now,
        TimeSpan.FromHours(1.0), "Appointment Subject");
    HourlyRecurrenceRule rrule = new HourlyRecurrenceRule(recurringAppointment.Start, 2, 10);
    recurringAppointment.RecurrenceRule = rrule;
    this.radScheduler1.Appointments.Add(recurringAppointment);
}

From the scheduler navigator change the time zone to any zone with "-". You will notice that some of the occurrences disappear.