We noticed a issue with version 11.0.126. In the top right corner, there is a button with an right arrow to close the sidebar on the right. Next to the button is a close button. When clicking on the button with arrow, the file got closed instead of hiding the right toolbar. Additional, he has a empty square box next to the close button. This doesn't apply to other browsers like Firefox or Chome. Since we're forced to support the IE as corporate browser, we need this fixed in IE.