TextField focus step over next field

I create a list of TextFields in Vertical layout. After view in UnityEditor, I use a Tab key to go to the next TextField.
But my focus go not to the next TextField. The focus goes one over next TextField
For example: From TextFiel0 focus goes to TextField2 then to Textfield4 and so on.

Simple source example to test:

Code (CSharp):

1. using UnityEngine;
2. using UnityEditor;
3. public class ExampleWindow : EditorWindow
4. {
5.  
6.     [MenuItem("MyWindows/ExampleWindow")]
7.     public static void Init()
8.     {
9.         GetWindow<ExampleWindow>();
10.     }
11.  
12.     void OnEnable()
13.     {
14.     }
15.  
16.     void OnGUI()
17.     {
18.         GUILayout.BeginVertical();
19.  
20.         for (int i = 0; i < 20; i++)
21.             EditorGUILayout.TextField("Text " + i);
22.  
23.         GUILayout.EndVertical();
24.         Repaint();
25.     }
26. }

I use Unity for Linux Version 2018.2.7f1
I do something wrong, or it is a bug in Unity?