Steps to reproduce:
1.Open attached project.
2.Open "main" scene.
3.Open "Game" tab
4.Drag "Game" tab to right and release it(take a look at attached GIF)
-UI element jumps up and stays there.

Sometimes when moving Game tab I was experiencing freezes and crashing, so I have attached Editor log also.

Problem:The UI fits out of game view when moving the Game tab.
Current result: UI behaving incorrectly.
Expected result: UI should not move.

Reproduced on: 5.4.0f1,5.4.0f3;
Works as expected: 5.4.0b21,5.3.5f1;