Switching between open documents doesn't work if clicked on the vey top of the file tabs.
I.e. when you on the middle of the tab, it gets active and you switch to the document. But if you at the very top of the tab (top edge of the window), nothing happens. Tabs should cover all the top part of the window, till the edge of the screen.
In other words, remove the gap between the top of the tab and top edge of the window.