To reproduce:
- Handle the CellFormatting event.
- Set CellElement Text property to a very long text.

Workaround:
Set CellElement MaxSize property like this:

void radScheduler1_CellFormatting(object sender, Telerik.WinControls.UI.SchedulerCellEventArgs e)
{
    e.CellElement.MaxSize =  new Size(150,23);
}

RadScheduler - there is no way change the style of drag item. Current embedded styling is hard to see in some themes.

Steps to reproduce:
1. Add a scheduler to a form.
2. Add some data and group it by resource.
3. Add a button and on click call the NavigateToNextResource method:
this.radSchedulerDemo.SchedulerElement.NavigateToNextResource();

You will see that nothing happens.

WORKAROUND:

RadScrollBarElement scrollBarElement = this.radScheduler1.SchedulerElement.ViewElement.Children[3] as RadScrollBarElement;
this.radScheduler1.SchedulerElement.NavigateToLastResource();
int numberOfBackSteps = scrollBarElement.Maximum - scrollBarElement.Value - (this.radSchedulerDemo.SchedulerElement.View.ResourcesPerView - 1);

for (int i = 0; i <= numberOfBackSteps; i++)
{
    this.radScheduler1.SchedulerElement.NavigateToPreviousResource();
}

Steps to reproduce.

1. Add a RadScheduler to a form, add some appointments.
2. Add grouping with at least two groups.
3. Drag an appointment from the second group (top to bottom) and drop it above the scheduler. The drag hint should be for invalid operation (striked red circle)
You will see that the appointment will disappear from the scheduler.

WORKAROUND
AddHandler Me.RadScheduler1.DragDropBehavior.Stopped, AddressOf DragDropBehavior_Stopped

Private Sub DragDropBehavior_Stopped(sender As Object, e As EventArgs)
    Dim element As TimelineGroupingByResourcesElement = Me.RadScheduler1.SchedulerElement.Children(0)

    For Each timelineViewElement In element.Children
        If timelineViewElement.GetType() = GetType(SchedulerTimelineViewElement) Then
            For Each applicationElement As RadElement In CType(timelineViewElement, SchedulerTimelineViewElement).Presenter.Children
                If applicationElement.GetType() = GetType(AppointmentElement) Then
                    applicationElement.Visibility = ElementVisibility.Visible
                End If
            Next
        End If
    Next
End Sub

RadScheduler printing does not take in consideration the Ruler scale and always print with 30 minutes timescale.

ScrollToWorkHours does not work properly in DayViewGroupedByResource mode

To work around the issue, you can set scheduler's GroupType to None, set the  ResourcesPerView property, set the GroupType to Resource:

radScheduler1.GroupType = GroupType.None;
this.radScheduler1.ActiveView.ResourcesPerView =resourcesPerView 
radScheduler1.GroupType = GroupType.Resource;

this.radScheduler1.Appointments.EndUpdate();

Does not refresh the Scheduler view element.

Steps to reproduce:
            radScheduler.ActiveViewType = SchedulerViewType.Timeline;
            radScheduler.GetTimelineView().ShowTimescale(Timescales.Hours);
            radScheduler.GetTimelineView().GetTimescale(Timescales.Hours).DisplayedCellsCount = 10;//set 8 for workarround.

            radScheduler.ActiveView.StartDate = DateTime.Today;
            radScheduler.GetTimelineView().RangeStartDate = DateTime.Today.AddHours(7);
            radScheduler.GetTimelineView().RangeEndDate = DateTime.Today.AddDays(1);
            radScheduler.GetTimelineView().ResourcesPerView = 5;

            radScheduler.GroupType = GroupType.Resource;
            radScheduler.SchedulerElement.SetResourceHeaderAngleTransform(SchedulerViewType.Timeline, 0);

Let's say that you have an appoiment that starts at 8:30 and ends at 8:30. RadScheduler will display it as it should, but it will not be considered by the printing functionality.
We should also have in mind the case where there are several appointments starting from 8:30 and ending at 8:30.

To reproduce:
RadSchedulerLocalizationProvider.CurrentProvider = new CustomSchedulerLocalizationProvider();

radScheduler1.Appointments.Add(new Appointment(DateTime.Now.AddDays(-5), DateTime.Now.AddDays(-4)));
radScheduler1.Appointments.Add(new Appointment(DateTime.Now.AddDays(5), DateTime.Now.AddDays(4)));

Workaround:
radScheduler1.SchedulerElement.Refresh();

The width of a resource does not always match the column(s) underneath it, resulting in the resources shifting to the left in relation to the column(s) below. It appears to be about 1 pixel  difference per resource which becomes more noticeable with multiple resources .If you resize the form the resources will come close to matching the column(s) before jumping back to the full difference again. This issue can be demonstrated in the Scheduler->Grouping demo

Currently, a time range of working ours is valid for all days in the week. There could be a rule that sets a specific range for some days of the week, leaving another range of hours for the rest of the days.

Steps to reproduce:
1. Add a RadSchduler to a form (No need to add appointments) 
2. Set the active view type to Timeline 
3. Set the Appointmentheight property of the timeline view element to 50 
4. Run the project, right-click on the scheduler and select Next View You will see a NullReferenceException exception.

The issue is when you drag up or drag down the top or bottom of the appointment i.e extend or decrease the slot.
The error I get with that same codebase is
Object reference not set to an instance of an object.
inner exception null

Source: Telerik.WinControls.Scheduler

StackTrace:
at Telerik.WinControls.UI.DayViewAppointmentsTable.appointment_MouseUp(Object sender, MouseEventArgs e)
   at Telerik.WinControls.UI.DayViewAppointmentsTable.AppointmentMouseUp(Object sender, MouseEventArgs e)
   at Telerik.WinControls.UI.RadSchedulerElement.scheduler_AppointmentElementMouseUp(Object sender, MouseEventArgs e)
   at Telerik.WinControls.UI.RadScheduler.OnAppointmentElementMouseUp(Object sender, MouseEventArgs args)...

1. Create a new project with RadScheduler.
2. Handle the AppointmentFormatting event and change appointment border color.
3. Run the project and add an appointment.

Use GetMultiDayView().Intervals.Add method to add intervals in multi day view. Set the time to be 0:00.

drop a scheduler on a form and call it schMain. replace your form1 code with the code below. it will reproduce the issue. in the load event of the form, there's a method called BindForm. if you comment out this line, it works. the resources are all in color like they should be. if you put the line back in, it breaks and they all go gray. i attached screen shots of what i see too.
Comment: You should map the Color property of ResourceMappingInfo class to the respective property in your business object in order to solve this issue.

If an appointment is about to change its resource, e.NewResourceId in the AppointmentDropping event should return the id new the new appointment. However, it returns nothing.

1. Create a new project with RadScheduler.
2. Add some resources.
3. Set GroupType property to Resource.
4. Handle AppointmentDropping event and print its NewResourceId property.
4. Run the project and add an appointment.
5. Try to move this appointment to another resource.