To reproduce:
this.radTextBoxControl1.Text = "dog and blue glue";
this.radTextBoxControl1.Size = new Size(50, 65);
this.radTextBoxControl1.Multiline = true;

Workaround:
use RadTextBox.

To reproduce:
public RadForm1()
{
    InitializeComponent();

    this.radTextBoxControl1.Text = "Sample text with misspelledd word";
    RadSpellChecker spellChecker1 = new RadSpellChecker();
    spellChecker1.AutoSpellCheckControl = radTextBoxControl1;
}

private void radTextBoxControl1_ContextMenuOpening(object sender, TreeBoxContextMenuOpeningEventArgs e)
{
    RadMenuItem customItem= new RadMenuItem("Custom item");
    e.ContextMenu.Items.Add(customItem);
}

Workaround: use RadTextBox instead:
RadSpellChecker spellChecker1 = new RadSpellChecker();    
this.radTextBox1.Text = "Sample text with misspelledd word";
spellChecker1.AutoSpellCheckControl = this.radTextBox1;
TextBoxSpellChecker tbSpellChecker = spellChecker1.GetControlSpellChecker(typeof(RadTextBox)) as TextBoxSpellChecker;
tbSpellChecker.DropDownMenu.DropDownOpening += DropDownMenu_DropDownOpening;

private void DropDownMenu_DropDownOpening(object sender, CancelEventArgs e)
{
    RadDropDownMenu menu = sender as RadDropDownMenu;
    RadMenuItem customItem = new RadMenuItem("Custom item");
    menu.Items.Add(customItem);
}

To reproduce:
1. Add ribbon with a tab, group and a RadTextBoxElement.
2. Open Edit UI Elements from the smart tag, select the TextBoxItem and set the MultiLine to true 
3. Run the app and the text box is not multiline

Workaround:
set it in code:             radTextBoxElement1.TextBoxItem.Multiline = true;

When you focus a RadTextBox you will notice the keyboard button that popups next to the focused control. However, for the RadAutoCompleteBox this keyboard button does not show.

Workaround: show it manually on the GotFocus event and hide it on the LostFocus event 

private void radTextBox1_GotFocus(object sender, EventArgs e)
{
    string progFiles = @"C:\Program Files\Common Files\Microsoft Shared\ink";
    string keyboardPath = Path.Combine(progFiles, "TabTip.exe");
    Process.Start(keyboardPath);
}
 
private void radTextBox1_LostFocus(object sender, EventArgs e)
{
    var procs = Process.GetProcessesByName("TabTip");
    if (procs.Length != 0)
        procs[0].Kill();
}

To reproduce:
- Select the time from the drop down and press close button.
- Notice that the form is deactivated.

Workaround:
void radTimePicker1_LostFocus(object sender, EventArgs e)
{
    this.Activate();
}

All controls (i.e. RadGridView, RadPropertyGrid, etc.), which use textbox editor, containing HostedTextBoxBase descendant, can be spelled by the RadSpellChecker. But the red underline is not displayed entirely. The inside hosted text box should have a bigger height.

To reproduce: 
- add a RadTextBox with empty Text property but NullText property has some value.
- change the Font style to Microsoft Sans Serif, 8.5pt. As a result the RadTextBox height is decresed a little and the NullText is cut off

Workaround: use Text property instead of NullText and cutomize its ForeColor to gray:
Font newFont = new Font("Microsoft Sans Serif", 8.5f);

public Form1()
{
    InitializeComponent();

    this.radTextBox1.Font = newFont;
    this.radTextBox1.Text = this.radTextBox1.NullText;
    this.radTextBox1.TextBoxElement.ForeColor = Color.Gray;
    this.radTextBox1.GotFocus+=radTextBox1_GotFocus;
    this.radTextBox1.LostFocus+=radTextBox1_LostFocus;

    this.radButton1.Select();
}

private void radTextBox1_LostFocus(object sender, EventArgs e)
{
   if (this.radTextBox1.Text==this.radTextBox1.NullText||this.radTextBox1.Text==string.Empty)
    {
        this.radTextBox1.Text = this.radTextBox1.NullText;
        this.radTextBox1.TextBoxElement.ForeColor = Color.Gray;
    }
    else
    {
         this.radTextBox1.TextBoxElement.ForeColor = Color.Black;
    }
}

private void radTextBox1_GotFocus(object sender, EventArgs e)
{
    if (this.radTextBox1.Text==this.radTextBox1.NullText)
    {
        this.radTextBox1.Text = string.Empty;
        this.radTextBox1.TextBoxElement.ForeColor = Color.Gray;
    }
    else
    {
         this.radTextBox1.TextBoxElement.ForeColor = Color.Black;
    }
}

When users select the "Ignore All" on the certain word the other ocupation of this word still market as wrong.

To reproduce: 

Populate the AutoCompleteBox and start a search returning enough results to need the scrollbar. When clicking and dragging the scroll bar to scroll - if the cursor is not positioned directly over the scrollbar at the time you release the mouseclick, the dropdown list is closed an item is added to the selection.

Workaround: 
 public partial class Form1 : Form
    {
        bool isMouseDown = false;

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            AddAutoCompleteItems();
            radAutoCompleteBox1.ListElement.VScrollBar.MouseDown += ListElement_MouseDown;
            radAutoCompleteBox1.ListElement.VScrollBar.MouseUp += ListElement_MouseUp;
            radAutoCompleteBox1.TokenValidating += radAutoCompleteBox1_TokenValidating;
        }

        void radAutoCompleteBox1_TokenValidating(object sender, TokenValidatingEventArgs e)
        {
            e.IsValidToken = !isMouseDown;
            isMouseDown = false;
        }

        void ListElement_MouseUp(object sender, MouseEventArgs e)
        {
            RadListVisualItem el = radAutoCompleteBox1.ListElement.ElementTree.GetElementAtPoint(e.Location) as RadListVisualItem;

            if (el != null)
            {
                return;
            }
            
            isMouseDown = false;
        }

        void ListElement_MouseDown(object sender, MouseEventArgs e)
        {
            isMouseDown = true;
        }

        private void AddAutoCompleteItems()
        {
            RadListDataItemCollection items = this.radAutoCompleteBox1.AutoCompleteItems;

            items.Add(new RadListDataItem("Joe Smith", "joe@fakecompany.com"));
            items.Add(new RadListDataItem("Adam Petersen", "adam@qwerty.com"));
            items.Add(new RadListDataItem("Jack Russel", "jack@russel.nocom"));
            items.Add(new RadListDataItem("Daniel Finger", "daniel.pinger@gmail.com"));
            items.Add(new RadListDataItem("Richard Vail", "rvail@richardvail.com"));
            items.Add(new RadListDataItem("Sebastian Jonnson", "s.jonnson@sjonnson.com"));
            items.Add(new RadListDataItem("Lee Cooper", "lee.cooper@coopercoorp.com"));
            items.Add(new RadListDataItem("Kelvin Clain", "kclain@clainkevin.com"));
            items.Add(new RadListDataItem("Maria Jenson", "mjenson@mariajenson.com"));
            items.Add(new RadListDataItem("Chelsea Maarten", "chelsea@maarten.com"));
            items.Add(new RadListDataItem("Jenson Chew", "jenson.chew@nospam.com"));
            items.Add(new RadListDataItem("Martin Williams", "m.williams@martinandwilliams.com"));
            items.Add(new RadListDataItem("Telerik", "clientservice@telerik.com"));
            items.Add(new RadListDataItem("James Stone", "james.stone@manystones.com"));
            items.Add(new RadListDataItem("Samuel Jackson", "samuel.jackson@nojackson.com"));
        }
    }

    public class MyRadAutoCompleteBox : RadAutoCompleteBox
    {
        protected override RadTextBoxControlElement CreateTextBoxElement()
        {
            return new MyRadAutoCompleteBoxElement();
        }
    }

    public class MyRadAutoCompleteBoxElement : RadAutoCompleteBoxElement
    {
        protected override TextBoxViewElement CreateViewElement()
        {
            return new MyAutoCompleteBoxViewElement();
        }

        protected override Type ThemeEffectiveType
        {
            get
            {
                return typeof(RadAutoCompleteBoxElement);
            }
        }
    }

    public class MyAutoCompleteBoxViewElement : AutoCompleteBoxViewElement
    {
        protected override int InsertTokenizedTextBlocks(int index, string text, bool performInvalidation)
        {
            bool isValid = performInvalidation ? this.OnTokenValidating(text) : true;

            if (!isValid)
            {
                return index;
            }
            return base.InsertTokenizedTextBlocks(index, text, performInvalidation);
        }

If the size of the text and icons on the screen is set to larger and the font of the text is set to 12 pixels. Letters that have tails below (such as: g, j, y) are not shown properly inside the text box. 

Workaround:

As a workaround one can set the minimum height of the text box to be as the height of the text and allow multi lines.

int textHeight = TextRenderer.MeasureText(this.radTextBox1.Text, this.radTextBox1.Font).Height;this.radTextBox1.TextBoxElement.TextBoxItem.MinSize = new Size(0, textHeight);this.radTextBox1.TextBoxElement.TextBoxItem.InvalidateMeasure();this.radTextBox1.TextBoxElement.TextBoxItem.UpdateLayout();this.radTextBox1.Multiline = true;

To reproduce:
- Drop RadMarkupDialog on the form
- In code set its DefaultFont and show it

WORKAROUND:
Create an instance of RadMarkupDialog prior showing it, not at design time.

Multiply line text is not correct align at the left side when control runs on Win xp.

Steps to reproduce:
this.radTextBoxControl1.Text = "This\nis a\ntest";

1. Create new project and add RadTextBox inside a user control.
2. Set its Dock property to Left.
3. Add custom button items in its layout by using RadButtonElement and StackLayoutElement.
4. Set a default value to the text box when handling the form Load event.
5. Run the project.

example:

Imports Telerik.WinControls.UI
Imports Telerik.WinControls.RichTextBox.Proofing
Imports System.IO
Imports System.Globalization

Public Class Form1

    Dim radTextBox1 As RadTextBox = New RadTextBox
    Dim radSpellChecker1 As RadSpellChecker = New RadSpellChecker

    Private Sub Form1_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
        radTextBox1.Parent = Me.Panel1
        radTextBox1.Multiline = True
        radTextBox1.Dock = DockStyle.Fill

        radSpellChecker1.SpellCheckMode = SpellCheckMode.WordByWord



        Dim textBoxControlSpellChecker As IControlSpellChecker = Me.radSpellChecker1.GetControlSpellChecker(GetType(RadTextBox))
        Dim documentSpellChecker As DocumentSpellChecker = TryCast(textBoxControlSpellChecker.SpellChecker, DocumentSpellChecker)
        Dim ms As New MemoryStream(My.Resources.sv_SE
                                   )
        Dim dictionary As New WordDictionary()
        dictionary.Load(ms)

        documentSpellChecker.AddDictionary(dictionary, CultureInfo.CurrentCulture)

        radSpellChecker1.SpellCheckMode = SpellCheckMode.AllAtOnce

    End Sub

    Private Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click
     
        Me.radSpellChecker1.Check(Me.radTextBox1)
    End Sub
End Class

Html formatting does not work as expected in design-time.