Changing the DataSource or scrolling are slow.

Create a grid with more than 20 columns and add 5K rows for example. Maximize the form and try to scroll with mouse wheel. You will notice that the scrolling performance is worse compared to the normal state of the form with less visible visual elements.

Workaround: this.radGridView1.EnableFastScrolling = true; and use the scrollbar's thumb

Second workaround: use paging:  https://docs.telerik.com/devtools/winforms/gridview/paging/overview Thus, you will display as many rows as possible to display on the screen per page. Instead of scrolling, you will navigate through pages.

FIX. RadDropDownList- when the form is started the textbox shows the end of the text instead of the begging of it, when the used text is longer than the control length.

FIX. RadGroupBox AutoSize property is not taken into consideration

Wrapping text in ColumnsGroupViewDefinition does not affect the size of the cells.

RadRichTextEditor renders the text with a little bigger characters spacing than RadRichTextBox and MS Word.
Note: this text spacing problem can be observed in other Telerik controls as well.

The HeaderText of the RadGridView columns is not properly serialized in the resource file for the corresponding language.

RadPageView has ten pages. Each page contains TableLayoutPanel (2 columns and 10 rows) and in each cell there is RadControl (textBox, checkbox etc). 

The result is that when pages are being changed, RadPageView show slow performance. Same scenario with standard controls works well.

Further investigations on the case show this:
"I had the same issue and I found other workaround. In my case I had TableLayoutPanel with RadSplittButton in each cell and each RadSplitButon was set as Dock = Fill. If I set AutoSize = false for RadSplitButton then the performance was ok and everything looks ok too."

To workaround this issue you should dispose the Instance property of RadMessageBox after each show of message box. For example:

WORKAROUND: 
RadMessageBox.Show("Text");
RadMessageBox.Instance.Dispose();

If you are using themes, consider the following approach:
            RadMessageBox.SetThemeName("Windows7");
            RadMessageBox.Show("This is some long text that sometimes does not wrap as it should.");
            var field = typeof(RadMessageBox).GetField("radMessageBoxForm", BindingFlags.NonPublic | BindingFlags.Static);
            field.SetValue(null, null);

When pressing the tab and RadDropDownList gets focus, there is no visual feedback to see which control has the focus.

1. Create a new project with RadGridView
2. Setup a hierarchy with a large number of rows
3. Apply grouping and expand all child views
4. Run the project and try to scroll

Steps to reproduce:
1. Add a form with RadPageView on it
2. Add RadPageViewPage
3. In the designer file there will be the following line: // TODO: Code generation for '' failed because of Exception 'Invalid Primitive Type: System.IntPtr. Consider using CodeObjectCreateExpression.'.

Our application embed a RadDock element.Unfortunately, in a non-systematic way, our application crash with this stack trace: 

Our application is a 64bit application (we migrated it to NET6 using Telerik 2022.2.510.60). As I told unfortunately in this case I'm not able to isolate the case in a simple project (as I'm used to to).

It would be useful by your side, however, make a check to the last trace line of the log I've gave to you: 

 at Telerik.WinControls.UI.ThemedFormBehavior.OnWMNCHitTest(Message& m)

If I decompile your code I find this:

L_param, returned in (1) is an IntPtr that, on a 64bit machine running a 64bit application could contains a value that SOMETIMES will crash in (2) where you try to convert it with an IntTo32 method...

99 time to 100 the code in line 755 works fine but I think that it is not guaranteed that L_Param returned in (1) can be fit in a 32bit box. This could explain why I use the phrase "...in a very random way" and why, at the moment, I'm not be able to give you a simple application where the problem is systematic.

I suspect that at line 755 we have got a problem, I'll appreciate your point of view about it.

To reproduce:
1.Add a RadGridView with one column.
2.Select the form and in the Properties window, set the form's Localizable property to true.
3.Specify the column's HeaderText for the default language.
4.Set the form's Language property to French (France).
5.Specify the column's HeaderText for  French (France).
6.Set the CurrentUICulture before the InitializeComponent method to "fr-FR". If you run the application, the column is localized as expected.
7.If you get back to the designer and change the form's Language property back to Default you will notice that the column's HeaderText disappears.

Workaround: set the HeaderText programmatically according to the current language.

RadGridView should support indexed full-text search out of the box.

Sorting of RadGridView slows down its performance when the control is used in self-reference hierarchy mode.

1. Drag a RadGridView to a form and dock it to fill the form.
2. Create and set a ColumnGroupsViewDefinition to the grid
3. Add data and run the project.
4. Resize the form and you will see that grid view layout would not look properly.
Also if your resize a column group only the first column in the group is resized while all others retain their widths.

Work around:
void radGridView1_SizeChanged(object sender, EventArgs e)
{
    this.InvalidateGridLayout();
}
 
private void InvalidateGridLayout()
{
    this.bllGridView1.TableElement.ViewElement.RowLayout.InvalidateLayout();
    this.bllGridView1.TableElement.InvalidateMeasure(true);
    this.bllGridView1.TableElement.UpdateLayout();
}

Controls in RadPanel redraw slowly when changing the Enabled state of the panel.

Workaround:

private void radButton1_Click(object sender, EventArgs e)
{
    if (this.radPanel1.Enabled)
    {
        this.radPanel1.Enabled = false;
    }
    else
    {
        this.radPanel1.Visible = false;
        this.radPanel1.Enabled = true;
        this.radPanel1.Visible = true;
    }
} 
 

The RadPdfViewer does not show text when pdf document is loaded.

When UseCompatibleTextRendering property is set to false, the data cells overlaps the row header cells when horizontal scrolling is performed.

To reproduce: please refer to the attached gif file.

The error is not reproduced each time with the Demo application. Sometimes an unhandled exception dialog appears and sometimes the application becomes unresponsive and you can not close the application with upper right X, the options to the right does not respond, you can not change demo using the list on the left. Selecting "Settings" in Property Grid section and then clicking on a boolean property (left column), scrolling using the mouse wheel, then selecting another property (with PropertyGridDropDownListEditor) or clicking around in the application (even outside of the property grid form).

Workaround:   this.radPropertyGrid1.EditorRequired += radPropertyGrid1_EditorRequired;

private void radPropertyGrid1_EditorRequired(object sender, PropertyGridEditorRequiredEventArgs e)
{
    if (e.EditorType == typeof(PropertyGridDropDownListEditor))
    {
        e.Editor = new CustomPropertyGridDropDownListEditor();
    }
}

public class CustomPropertyGridDropDownListEditor : PropertyGridDropDownListEditor
{
    public override object Value
    {
        get
        {
            PropertyGridItemElement element = this.OwnerElement as PropertyGridItemElement;
            PropertyGridItem item = element.Data as PropertyGridItem;
            if (item == null)
            {
                return null;
            }
            return base.Value;
        }
        set
        {
            base.Value = value;
        }
    }
}