How to reproduce: the issue is only reproducible in client`s environment, Windows 10 build 1607
Public Class Form1

    Sub New()
        InitializeComponent()

    End Sub

    Protected Overrides Sub OnLoad(e As EventArgs)
        MyBase.OnLoad(e)

        Me.RadGalleryElement1.MaxRows = 1

        For i As Integer = 0 To 149
            Dim blueItem1 As New RadGalleryItem("", My.Resources.RibbonBar_GettingStarted_CreatingAGallery001)
            Me.RadGalleryElement1.Items.Add(blueItem1)
        Next
    End Sub

End Class

Workaround: 
Public Class Form1

    Sub New()
        InitializeComponent()

        AddHandler Me.RadGalleryElement1.DropDownOpening, AddressOf RadGalleryElement1_DropDownOpening

    End Sub

    Protected Overrides Sub OnLoad(e As EventArgs)
        MyBase.OnLoad(e)

        Me.RadGalleryElement1.MaxRows = 1

        For i As Integer = 0 To 149
            Dim blueItem1 As New RadGalleryItem("", My.Resources.RibbonBar_GettingStarted_CreatingAGallery001)
            Me.RadGalleryElement1.Items.Add(blueItem1)
        Next
    End Sub

    Private Sub RadGalleryElement1_DropDownOpening(sender As Object, e As System.ComponentModel.CancelEventArgs)
        Dim gallery = DirectCast(sender, RadGalleryElement)
        Dim popup = gallery.GalleryDropDown.PopupElement
        Dim wa = Screen.PrimaryScreen
        popup.Children(0).MaxSize = New Size(0, wa.Bounds.Height)

    End Sub

End Class

To reproduce:
1.Add a RadRibbonBar (with several groups and buttons inside a group) and a theme (i.e. TelerikMetro).
2.Apply the theme for the RadRibbonBar: setting the ThemeName property to "YourThemeName".
for example: this.radRibbonBar1.ThemeName = "TelerikMetro";
3. Run the application and resize the form in a way to collapse all ribbon groups. When you open the popup for the group, all popup elements are with incorrect style.

Workaround: load the theme in the form's constructor.

You have a scenario where there is a maximized MDI child form in a RadRibbonForm. You try to close the maximized child form from the MDI box of RadRibbonBar, but instead of getting the form closed, you programmatically hide it, so that you can reuse it further. The moment you try to show that form again, it appears non-maximized which is not a correct behavior.

To reproduce:
- Add complex controls to the backstage pages (add at least 4 pages).
- Change the pages at runtime.

Workaround:
Private Sub RadRibbonBarBackstageView1_BackstageViewOpening(sender As Object, e As System.ComponentModel.CancelEventArgs) Handles RadRibbonBarBackstageView1.BackstageViewOpening
    BackstageViewPage1.Visible = True
    BackstageViewPage2.Visible = True
    BackstageViewPage3.Visible = True
    BackstageViewPage4.Visible = True
End Sub

Set the RadGalleryElement.DropDownSizingMode property to Telerik.WinControls.UI.SizingMode.None. however, you will notice that when the gallery's popup is opened, the grip is visible. Please refer to the attached project.

Workaround:

Sub New()
    
    InitializeComponent()

    AddHandler Me.RadGalleryElement1.DropDownOpened, AddressOf DropDownOpened

End Sub

Private Sub DropDownOpened(sender As Object, e As EventArgs)
    Me.RadGalleryElement1.GalleryPopupElement.SizingGrip.SizingMode = Telerik.WinControls.UI.SizingMode.None
End Sub

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:
- 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:

1. Collapse the ribbon
2. Select the tab to show the popup
3. Type some text in the RadDropDownListElement
4. Press Escape, Enter, Backspace keys. You will notice that these keys are not handled by the drop down. However, the ribbon popup is closed and there is no way to handle these keys.

Workaround: set the AutoScaleMode property of UserControl to None.

Please refer to the attached gif file.

Workaround: close manually the popup by calling the this.radSplitButtonElement1.DropDownMenu.ClosePopup(Telerik.WinControls.UI.RadPopupCloseReason.Mouse) method.

To reproduce:

 public Form1()
 {
     InitializeComponent();

     this.radRibbonBar1.CollapseRibbonOnTabDoubleClick = false;
 }

Workaround:

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

Use the attached project to reproduce.

Workaround:
private void RadForm1_SizeChanged(object sender, EventArgs e)
{
    if (this.WindowState == FormWindowState.Normal)
    {
        this.SizeChanged -= RadForm1_SizeChanged;
        this.Size = new Size(this.Size.Width + 1, this.Size.Height + 1);
        this.Size = new Size(this.Size.Width - 1, this.Size.Height - 1);

        this.SizeChanged += RadForm1_SizeChanged;
    }
}

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:
Add RadRibbonForm and change the theme(for example to WIndows8Theme). Run the project. The system buttons are covered by the fill of RadRibbonBarElement.

Workaround:
Set the DrawFill property of RadRibbonBarElement to false.
this.RibbonBar.RibbonBarElement.DrawFill = false;

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;
    }
}

When Windows aero effects are enabled and the form width is being decreased, the title bar text appears over the title bar buttons and further more when continuing reducing the width of the form the buttons disappear and a small black rectangle is shown instead.

To reproduce:
- Set the Windows theme to Windows 7 Basic
- Start a RadRibbonForm and maximize it

Workaround:

void Form1_Resize(object sender, System.EventArgs e)
{
    if (this.WindowState == FormWindowState.Maximized)
    {
        this.RibbonBar.RibbonBarElement.IconPrimitive.Padding = new Padding(5, 5, 0, 0);
    }
    else
    {
        this.RibbonBar.RibbonBarElement.IconPrimitive.Padding = Padding.Empty;
    }
}

To reproduce: 
1. Add a RadRibbonBar and a RadButtonElement in one of the groups.
2. Set the RadButtonElement.UseCompatibleTextRendering property is set to false.
3. Set the RadButtonElement.Enabled property to false.

You will notice that the text is hardly read compared to version Q2 2014.

Workaround: Currently, the possible solution is to set the RadButtonElement.UseDefaultDisabledPaint property to false and subscribe to the EnabledChanged event where you can modify the ForeColor in order to make it gray when the button is disabled and apply a gray scaled image.