Steps to reproduce a problem:
1) Add RibbonControlAdv to the form.
2) Add ToolStripTabItem.
3) Add ToolStripEx on ToolStripTabItem.
4) Add DropDownButton on ToolStripEx and add some items to DropDown button.
5) Run the form and add your DropDown button to quick access toolbar using right mouse button popup menu.
6) Click your dropdown button on quick acces toolbar.
7) Remove the button from quick access toolbar.
8) Now click your button on ToolStripEx and you'll see that button menu does not appear or is displayed in wrong position.
There is a video attached to show the problem.
DropDownButton Video.zip