To reproduce:
public RadRibbonForm1()
{
    InitializeComponent();
    radRibbonBar1.Expanded = false;
}     

private void button1_Click(object sender, EventArgs e)
{
    if (ribbonTab2.Visibility == Telerik.WinControls.ElementVisibility.Visible)
    {
        ribbonTab2.Visibility = Telerik.WinControls.ElementVisibility.Collapsed;
    }
    else
    {
        ribbonTab2.Visibility = Telerik.WinControls.ElementVisibility.Visible;
    }
}

Workaround:
private void button1_Click(object sender, EventArgs e)
{
  
    this.radRibbonBar1.RootElement.SuspendLayout();
    if (ribbonTab2.Visibility == Telerik.WinControls.ElementVisibility.Visible)
    {
        ribbonTab2.Visibility = Telerik.WinControls.ElementVisibility.Collapsed;
    }
    else
    {
        ribbonTab2.Visibility = Telerik.WinControls.ElementVisibility.Visible;
    }
    this.radRibbonBar1.RootElement.ResumeLayout(false);          
}

I have a RadGalleryElement in my RadRibbonBar.  It has both a minimum and maximum row count of four, and currently contains 6 items.  I have "selection" enabled for the Gallery.  The selection states persist for the first row of items, but do not for my second row.

To reproduce:

1. Add a RadRibbonBar with a RadDropDownListElement and some other elements.
2. Use the following code:

for (int i = 0; i < 5; i++)
{
    RadListDataItem item = new RadListDataItem();
    item.Text = "Item" + i;
    this.radDropDownListElement1.Items.Add(item);
}
this.radRibbonBar1.EnableKeyMap = true;
this.radDropDownListElement1.KeyTip = "S";         
this.radDropDownListElement1.DropDownStyle = Telerik.WinControls.RadDropDownStyle.DropDownList; 
3. Press Alt, then 2. You will see the key tips for the drop down and its sibling items. 
4. Press S. You are expected to be navigated to the RadDropDownListElement, but are not. 

Here it is illustrated the behavior: http://screencast.com/t/Qmvqufznjt

To reproduce:
1.Create a new Visual C# -> Telerik Windows Forms Application
2.Drag a RadRibbonBar control onto RadForm1
3.Create a single tab "First Tab" (otherwise you cannot collapse the ribbon)
4.Drag a button onto the form and add the following code to the click event handler:
RibbonTab tab = new RibbonTab("Test");
this.radRibbonBar1.CommandTabs.Add(tab);
tab.IsSelected = true;
5.You should end up with something like the attached png file.
6.Run the project and click the button. You should see the new tab is created and selected.
7.Close the project and run it again. This time, collapse the ribbon before clicking the button. No new tab is visible on the ribbon. Even if you click on the [First Tab] to show the full ribbon.
8.Click the expand ribbon button on the right and the new tab will then appear.

Workaround:
bool isExpanded = this.radRibbonBar1.Expanded;
this.radRibbonBar1.Expanded = true;
RibbonTab tab = new RibbonTab("Test " + this.radRibbonBar1.CommandTabs.Count); 
this.radRibbonBar1.CommandTabs.Add(tab);
tab.IsSelected = true;
this.radRibbonBar1.Expanded = isExpanded;

To reproduce:
- Set the theme and show the help button.

Workaround:
Hide the fill and the border in Visual Style builder

Workaround:

public Form1()
{
    InitializeComponent();
     
    this.radRibbonBar1.KeyTipShowing+=radRibbonBar1_KeyTipShowing;
}

private void radRibbonBar1_KeyTipShowing(object sender, CancelEventArgs e)
{
    RadButtonElement b = sender as RadButtonElement;
    if (b!=null && b.Enabled==false)
    {
        e.Cancel = true;
    }
}

To reproduce:

public partial class Form2 : RadRibbonForm
{
    public Form2()
    {
        InitializeComponent(); 

        this.WindowState = FormWindowState.Maximized;
        this.radRibbonBar1.ApplicationMenuStyle = ApplicationMenuStyle.BackstageView;
        this.AllowAero = false;         
        this.Icon = Properties.Resources.WinFormsIcon;     
    }
}

Workaround1: set AllowAero property to true if it is possible.
Workaround2: this.radRibbonBar1.RibbonBarElement.RibbonCaption.MouseMove += RibbonCaption_MouseMove;
private void RibbonCaption_MouseMove(object sender, MouseEventArgs e)
{
    if (e.Button == System.Windows.Forms.MouseButtons.Left && this.WindowState== FormWindowState.Maximized)
    {
        this.WindowState = FormWindowState.Normal;
        this.Location = new Point(this.Location.X,e.Location.Y);
    }
}

How to reproduce: set a size in the designer, when the form loads its size will not be the same as the one set

Workaround: set the size in the Load event of the ribbon form

private void Form_Shown(object sender, EventArgs e)
{
	this.Size = new Size(600, 600);
}

If I left-click on one of tab header, the related tab expand itself showing all the contained items.
But, if I expand the tab using the mouse right button, the tab expand itself but it appears blank!

Workaround:

private void radRibbonBar1_MouseDown(object sender, MouseEventArgs e)
{
    RibbonTab tab = this.radRibbonBar1.ElementTree.GetElementAtPoint(e.Location) as RibbonTab;
    if (tab!=null && e.Button== System.Windows.Forms.MouseButtons.Right)
    {
        tab.IsSelected = true;
    }
}

Workaround: set the AutoScaleMode property of UserControl to None.

To reproduce:
- Add ribbon bar to a form and set its IsMdiContainer property to true.
- Add an MDI child with a ribbon bar and minimize it.

To reproduce: add 3 ribbon tabs at design time and use the following code snippet:

public Form1()
{
    InitializeComponent(); 
}

private void InsertTabs()
{
    for (int i = 1; i <= 5; i++)
    {
        var index = radRibbonBar1.CommandTabs.IndexOf(this.ribbonTab3);
        radRibbonBar1.CommandTabs.Insert(index, new RibbonTab(string.Format("Tab {0}", i.ToString())));
    }
}

private void Form1_Load(object sender, EventArgs e)
{
    InsertTabs();
}

Workaround: insert the tabs in the form's constructor.

To reproduce:
1. Open the demo app on a remote machine
2. Click on the local machine to move the focus to it 
3. Hold down Alt key
4. Click on the demo app on the remote machine
5. Release the Alt key => the keytips are shown, while they shouldn't as KeyDown was not on that machine

To reproduce:

 public Form1()
 {
     InitializeComponent();

     this.radRibbonBar1.CollapseRibbonOnTabDoubleClick = false;
 }

Workaround:

if (this.radRibbonBar1.CommandTabs.Count > 0)
{
    this.radRibbonBar1.CollapseRibbonOnTabDoubleClick = false;
}

1. Place a RadRibbonBar on a form

2. Add couple of New Tabs

3. Select a tab in Design Time

4. You will see that the current tab is not switched

Note that you can switch to a different tab if you click it 3 times or if you fast click twice on a tab and then select another tab.

To reproduce:
- Add a RadToggleButtonElement to the quick access toolbar.

Workaround:
RadToggleButton button = new RadToggleButton();
button.Text = "Test";        
button.Height = 17;

RadHostItem host = new RadHostItem(button);
host.MinSize = new Size(50, 0);
host.MaxSize = new Size(0, 17);
host.StretchVertically = false;

radRibbonBar1.QuickAccessToolBarItems.Add(host);

To reproduce:
Open a form with a ribbon, focus the tabs and press 1 with the screen keyboard (German language). 

Workaround:
class MyRibbon : RadRibbonBar
{
    protected override ComponentInputBehavior CreateBehavior()
    {
   
        return new MyComponentBehavior(this);
    }
    public override string ThemeClassName
    {
        get { return typeof(RadRibbonBar).FullName; }
    }
}
class MyComponentBehavior : RibbonBarInputBehavior
{
    public MyComponentBehavior(RadRibbonBar owner) : base(owner)
    {

    }
    protected override string GetKeyStringRepresentation(Keys input)
    {
        uint nonVirtualKey = NativeMethods.MapVirtualKey((uint)input, 2);

        if (nonVirtualKey > char.MaxValue)
        {
            return null;
        }

        return base.GetKeyStringRepresentation(input);
    }
}

In RadDropDownListElement add two DescriptionTextListDataItem:

            radDropDownListElementFoo.Items.Add(new DescriptionTextListDataItem("Foo 1", "Description 1"));
            radDropDownListElementFoo.Items.Add(new DescriptionTextListDataItem("Foo 2", "Description 2"));

But the description is not displayed and the drop down height is too large (foo.png)

What am I doing wrong?

If change ItemHeight = 36, then description is displayed, but the drop down height is too large (foo36.png)

Please refer to the attached sample project and follow the steps from the gif file. 

Shrink the ribbon to create sub groups for expanding. Then, maximize the form. You will notice that the groups are still collapsed although there is so much space.

When changing the layout mode and a button has no text an exception occurs.

Workaround: 

- Set the text of all buttons to an empty string.