Please refer to the attached screenshot.

Workaround: use a RadForm without RadRibbonFormBehavior and hide the FormElement.TitleBar.

To reproduce:
public partial class Form1 : RadForm
{
    public Form1()
    {
        InitializeComponent();
        this.IsMdiContainer = true;
    }

    private void radButton1_Click(object sender, EventArgs e)
    {
        RadForm childForm = new RadForm();
      
        childForm.Text = "MDI Child " + DateTime.Now.ToShortTimeString();
        childForm.MdiParent = this;
        childForm.WindowState = FormWindowState.Maximized;
        childForm.Show();
    }
}

To reproduce:
- Create blank WinForms RadForm Application.
- Set WindowState property to Maximized.
- Add RadGroupBox to the form. Set equal space on all sides.
- Anchor the group box to all sides.
- Launch application - spacing around outside of group box is incorrect.
-  Restore form to normal size - spacing around group box is incorrect.

Workaround:
radGroupBox1.Dock = DockStyle.Fill;
radGroupBox1.GroupBoxElement.Margin = new Padding(20);

For the time being to show the grid I would recommend you to use an empty RadStatusStrip.

To reproduce:
1.Add a RadButton and on its Click event, show a RadMessageBox.
2.Add a RadDropDownList .
3.Drag several themes from the toolbox and drop them onto the form (e.g. Office2010Black, Office2010Blue, TelerikMetro, Windows8)
4.Use the following code:

public Form1()
{
    InitializeComponent();

    this.radDropDownList1.Items.Add("Office2010Black");
    this.radDropDownList1.Items.Add("Office2010Blue");
    this.radDropDownList1.Items.Add("TelerikMetro");
    this.radDropDownList1.Items.Add("Windows8");

    this.radDropDownList1.SelectedIndexChanged += radDropDownList1_SelectedIndexChanged;
    this.radDropDownList1.SelectedItem = this.radDropDownList1.Items[0];
}

private void radDropDownList1_SelectedIndexChanged(object sender,
    Telerik.WinControls.UI.Data.PositionChangedEventArgs e)
{
    string itemText = this.radDropDownList1.Items[e.Position].Text;           
    ThemeResolutionService.ApplicationThemeName = itemText;
}

private void radButton1_Click(object sender, EventArgs e)
{
    RadMessageBox.Show("Some message", "Confirmation", MessageBoxButtons.OKCancel);
}

When you select a new item from the RadDropDownList, the theme for the entire application is changed. But when you click the button to show a RadMessageBox, the RadMessageBox has incorrect style for its buttons.

Workaround: set the RadMessageBox.ThemeName before showing it:

RadMessageBox.ThemeName = ThemeResolutionService.ApplicationThemeName;
RadMessageBox.Show("Some message", "Confirmation", MessageBoxButtons.OKCancel);

To reproduce:

Create a RadFrom, make it MDIParent and add MDI children Set the RightToLeft property of the MDIParent to Yes and you will see that the the left side of the child forms is a little cut off. This can be seen by comparing the distance between the end of the form and the X button.

RadMessageBox - Buttons are not arranged correctly in RTL

Workaround: use RadRibbonForm instead or set minimum and maximum size

To reproduce:

1. Open a RadForm
2. Maximize the form.
3. Restore the form. Then we can see odd line on the bottom of title bar / top of the form.  If you resize the form (make it bigger), new visible areas of form doesn't contain this weird line.

Workaround:
protected override void WndProc(ref Message m)
{
    FormWindowState currentWindowState = this.WindowState;
    base.WndProc(ref m);
    if (currentWindowState == FormWindowState.Maximized && this.WindowState== FormWindowState.Normal)
    {
      
        this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.SizableToolWindow;
        this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.Sizable;
    }
}      

To reproduce:

Create a RadForm and set the property as follows:

public Form1()
{
    InitializeComponent();
    this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.FixedToolWindow;
}

Workaround:

Set the ShowIcon property to false:

public Form1()
{
    InitializeComponent();
    this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.FixedToolWindow;
    this.ShowIcon = false;
}

To reproduce:

Show RadMessageBox as follows:

RadMessageBox.Show(this, "מסר כלשהו", "Caption", MessageBoxButtons.OKCancel, RadMessageIcon.Error, MessageBoxDefaultButton.Button1, RightToLeft.Yes, "מסר2 כלשהו");

Open the details button and you will see that the text is כלשהו מסר2

To reproduce:

Create a RadForm and use the following code:

public Form1()
{
    InitializeComponent();

    var theme = new Telerik.WinControls.Themes.Windows7Theme();
    ThemeResolutionService.ApplicationThemeName = theme.ThemeName;// "Windows7";
    this.AllowTheming = false;
}

Start the application on Windows 7, you will see that the close/minimize/maximize buttons cannot be clicked.

Workaround:

Do not set the AllowTheming property or set it to true

Description: Text alignment of the title bar caption can not be changed. 

this.FormElement.TitleBar.TitlePrimitive.Alignment = ContentAlignment.MiddleCenter;

1. Create a new project and add a button.
2. On button click show a new RadForm by calling its ShowDialog method from another thread. You should use Invoke.

1. Create a new project with RadForm and RadGridView.
2. Handle the ScreenTipNeeded event to show screen tips in RadGridView cells.
3. Run the project and note that the first time when showing a screen tip, RadForm changes its size.

FIX. RadForm - setting the CancelButton property of the form to a button named exactly CancelButton, will prevent the button click event from firing when Esc is pressed. Changing the name of the button anything else will resolve the case.
Comment: This is the default beavior of the standard button and comes from .NET Framework.

FIX. Pressing Escape does not trigger the Click event of the form's CancelButton.

To reproduce:
- Add RadForm
- Set RightToLeft = True
- Click the form icon (the title bar icon) => the menu appears on the left side of the form instead of the right side. And also the menu is not in right to left mode.

Steps to reproduce.

1. Add a grid and a button to a form.
2. Set the button as the AcceptButton
3. Add a text column to the grid
4. Run the project, open a cell for edit, hit enter and the button will be clicked closing the form in the process.

Form should be closed only with Left mouse button