To reproduce:
 public Form1()
 {
     InitializeComponent();

     for (int i = 0; i < 7; i++)
     {
         this.radScheduler1.Appointments.Add(new Appointment(DateTime.Now.AddHours(i),TimeSpan.FromHours(3),"App" + i));
     }
     this.radScheduler1.AutoSizeAppointments = true;
     this.radScheduler1.ActiveViewType = SchedulerViewType.Month;
     SchedulerMonthView monthView = this.radScheduler1.GetMonthView();
    
     monthView.EnableAppointmentsScrolling = true;
 }

Workaround: set the AutoSizeAppointments property to false.