menupopup shifts position when timer event occurs

If a menupopup is shown such that submenu is displayed to the left of the parent menu, then next time a timer event occurs the submenu will jump to the right side of the parent menu. This makes selecting items difficult.

zkfiddle:
http://zkfiddle.org/sample/14qvh7u/4-timer-causes-menupopup-to-shift-position