Please refer to the attached gif file demonstrating how to reproduce the problem.

Workaround: close the popup when pressing Backspace:

 this.radTextBox1.TextBoxElement.TextBoxItem.TextBoxControl.KeyDown+=TextBoxControl_KeyDown;
private void TextBoxControl_KeyDown(object sender, KeyEventArgs e)
{
    if (e.KeyData== Keys.Back)
    {
        TextBoxSpellChecker textBoxSpellChecker = _radSpellChecker.GetControlSpellChecker(typeof(RadTextBox)) as TextBoxSpellChecker;
        if (textBoxSpellChecker!=null)
        {
            textBoxSpellChecker.DropDownMenu.ClosePopup(RadPopupCloseReason.Keyboard);
        }
    }
}

To reproduce:
- Set the mask to IP.
- Change the culture to German.

Workaround:
Set the Culture of the RadMaskedEditBox to English.

Workaround:
this.radTextBox1.TextBoxElement.Fill.BackColor = backColor;
this.radTextBox1.TextBoxElement.BackColor = backColor;

The value set to the last spin editor is overridden with its previous value. 

How to reproduce: check the attached videos

Workaround: 
 public partial class Form1 : Form
 {
     public Form1()
     {
         InitializeComponent();

         this.radColorBox1.ValueChanging += radColorBox1_ValueChanging;
         ((RadForm)this.radColorBox1.ColorBoxElement.ColorDialog.ColorDialogForm).FormClosing += Form1_FormClosing;
     }

     bool cancelValueChange;
     Telerik.WinControls.UI.RadColorPicker.ProfessionalColors professionalColors;
     private void Form1_FormClosing(object sender, FormClosingEventArgs e)
     {
         Control colorSelector = this.radColorBox1.ColorBoxElement.ColorDialog.ColorDialogForm.RadColorSelector;
         RadPageView pageView = colorSelector.Controls[3] as RadPageView;
         if (pageView.SelectedPage.TabIndex == 3)
         {
             cancelValueChange = true;
             professionalColors = pageView.Pages[3].Controls[0] as Telerik.WinControls.UI.RadColorPicker.ProfessionalColors;
         }
         else
         {
             professionalColors = null;
         }
     }

     private void radColorBox1_ValueChanging(object sender, Telerik.WinControls.UI.ValueChangingEventArgs e)
     {
         if (cancelValueChange && professionalColors != null) 
         {
             e.Cancel = true;

             RadSpinEditor alphaSpinEditor = professionalColors.Controls[12] as RadSpinEditor;
             RadSpinEditor redSpinEditor = professionalColors.Controls[15] as RadSpinEditor;
             RadSpinEditor greenSpinEditor = professionalColors.Controls[11] as RadSpinEditor;
             RadSpinEditor blueSpinEditor = professionalColors.Controls[7] as RadSpinEditor;
             cancelValueChange = false;

             this.radColorBox1.Value = Color.FromArgb((int)alphaSpinEditor.Value, (int)redSpinEditor.Value, (int)greenSpinEditor.Value, (int)blueSpinEditor.Value);
             
         }
     }
 }

To reproduce:
1) Create RAD FORM (Project)
2) Add a TableLayoutPanel
3) In 1 cell add TextBox and change the font... it expands.
4) In cell 2 add a RadTextBox and change the font. The control is not resized.

In addition RatTextBox has correct size at runtime. 

To reproduce:

            this.radDateTimePicker1.MinDate = DateTime.Now;
            this.radDateTimePicker1.MaxDate = DateTime.Now;

Please refer to the attached screenshots. Although the user is not allowed to change the selection, the future dates are not grayed out as the dates before the MinDate.

Workaround:

public RadForm1()
{
    InitializeComponent();

    this.radDateTimePicker1.MinDate = DateTime.Now;
    this.radDateTimePicker1.MaxDate = DateTime.Now;

    RadDateTimePickerCalendar calendarBehavior = this.radDateTimePicker1.DateTimePickerElement.GetCurrentBehavior() as RadDateTimePickerCalendar;
    calendarBehavior.Calendar.ElementRender += Calendar_ElementRender; 
}

private void Calendar_ElementRender(object sender, RenderElementEventArgs e)
{
    if (e.Day.Date > this.radDateTimePicker1.MaxDate.Date || e.Day.Date < this.radDateTimePicker1.MinDate.Date)
    {
        e.Element.Enabled = false;
    }
    else
    {
        e.Element.Enabled = true;
    }
}

How to reproduce:
1. Install Telerik Controls (version: 2016.3.1024)
2. Launch Visual studio. Create Windows application project.
3. Drop RadPopupContainer from the toolbox on to the windows form. Save the form.
4. Mouse click on the control on design canvas to select RadScrollablePanelContainer panel.
5. Now click on smart tag of RadScrollablePanelContainer panel and select "Undock in parent container" option.
6. Now separate RadScrollablePanelContainer panel by moving it to some location on the form. Save the form.
7. Try to move RadPopupContainer. Observe that it does not allow to move.
8. Click on the smart tag of RadScrollablePanelContainer panel and select "Dock in parent" option. Observe that  the RadScrollablePanelContainer panel is not docked into the RadPopupContainer control.

To reproduce:
- Add RichTextBox and type two words each on a separate line.
- Perform spell check using the following code:

radSpellChecker1.SpellCheckMode = SpellCheckMode.WordByWord;
radSpellChecker1.Check(richTextBox1);

The result is shown on the attached image.

Workaround: use simple data binding with the editor and its Text property

this.radCalculatorDropDown1.CalculatorElement.EditorContentElement.TextBoxItem.DataBindings.Add("Text", testObject, "TestValue", false, DataSourceUpdateMode.OnPropertyChanged);

How to reproduce:
 this.radMaskedEditBox1.Font = new System.Drawing.Font("Segoe UI", 20F);

 this.radMaskedEditBox1.MaskType = Telerik.WinControls.UI.MaskType.Standard;
 this.radMaskedEditBox1.Mask = "#####-######";
 this.radMaskedEditBox1.Value = "47997006886";


Workaround: 
this.radMaskedEditBox1.Font = new System.Drawing.Font("Segoe UI", 20F);

this.radMaskedEditBox1.MaskType = Telerik.WinControls.UI.MaskType.Standard;
this.radMaskedEditBox1.Mask = "#####-######";
this.radMaskedEditBox1.Text = "47997006886";

To reproduce: please refer to the attached sample project and gif file.

Workaround: this.radTextBox1.MinimumSize = new System.Drawing.Size(0, 25);
or
Use RadTextBoxControl

To reproduce: 
1. Enter some text and click the first button. Both properties, Text and Value contain the expected value.
2. Click the second button to clear the text and value.
3. Enter some text again and click the first button. You will notice that the Value remains empty. 

public RadForm1()
{
    InitializeComponent();

    this.radMaskedEditBox1.MaskType = Telerik.WinControls.UI.MaskType.None;
    this.radMaskedEditBox1.Mask = "CCCCCCC";
}

private void radButton1_Click(object sender, EventArgs e)
{
    this.radLabel1.Text = "Text: " + this.radMaskedEditBox1.Text;
    this.radLabel2.Text = "Value: " + this.radMaskedEditBox1.Value + "";
}

private void radButton2_Click(object sender, EventArgs e)
{
    this.radMaskedEditBox1.Clear();
}

Workaround: use MaskType.Standard

Workaround:

class MyTextBoxInputHandler : TextBoxInputHandler
{

public MyTextBoxInputHandler(RadTextBoxControlElement el) : base(el)
{
}

public override bool ProcessMouseWheel(MouseEventArgs e)
{
return false;
}
}

 radTextBoxControl1.TextBoxElement.InputHandler = new MyTextBoxInputHandler(radTextBoxControl1.TextBoxElement);

How to reproduce:
Just open the popup with the Alt and Down arrow key combination, you will notice that the value changes

Workaround: 
public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
        this.radDateTimePicker1.DateTimePickerElement.KeyDown += DateTimePickerElement_KeyDown;
    }

    private void DateTimePickerElement_KeyDown(object sender, KeyEventArgs e)
    {
        if (e.KeyCode == Keys.F4 || (e.KeyData == (Keys.Alt | Keys.Down)))
        {
            e.Handled = true;
        }
    }
}

Workaround: 

public RadForm1()
{
    InitializeComponent();

    this.radSpinEditor1.SpinElement.TextChanging += SpinElement_TextChanging;
    this.radSpinEditor1.TextChanged += radSpinEditor1_TextChanged;
}

private void SpinElement_TextChanging(object sender, Telerik.WinControls.TextChangingEventArgs e)
{
    int numericValue = 0;
    if (!int.TryParse(e.NewValue, out numericValue))
    {
        this.radSpinEditor1.Tag = e.OldValue;
        e.Cancel = false;
    }
}

private void radSpinEditor1_TextChanged(object sender, EventArgs e)
{
    if (this.radSpinEditor1.Tag != null)
    {
        this.radSpinEditor1.SpinElement.Text = this.radSpinEditor1.Tag.ToString(); 
        this.radSpinEditor1.Tag = null;
    }
}

To reproduce:
 radTimePicker1.Value = DateTime.Now.AddDays(10);
 radTimePicker1.TimePickerElement.MaskedEditBox.MaskType = Telerik.WinControls.UI.MaskType.FreeFormDateTime;

Workaround:

protected override void OnLoad(EventArgs e)
{
    base.OnLoad(e);
    radTimePicker1.Value = DateTime.Now.AddDays(10);

    var provider = radTimePicker1.TimePickerElement.MaskedEditBox.Provider as FreeFormDateTimeProvider;

    provider.MinDate = DateTime.MinValue;
    provider.MaxDate = DateTime.MaxValue;
}

To reproduce: run the attached sample project, open the popup and try to to scroll the grid with using the mouse wheel. You will notice that the popup is immediately closed.

Workaround: 
    Private Sub PopupClosing(sender As Object, args As Telerik.WinControls.UI.RadPopupClosingEventArgs)
        If args.CloseReason = Telerik.WinControls.UI.RadPopupCloseReason.Mouse Then
            args.Cancel = True
        End If
    End Sub