Ubuntu: event handler called not in time: control.addEventHandler(DRAG_EXITED_TARGET, and ... DRAG_EXITED

handler, added to some control via "control.addEventHandler(DRAG_EXITED_TARGET, ..."
should be called when mouse exits out of control border.
this is actually work as expected on Windows, but not on Ubuntu.

on Ubuntu, handler is called right after drag started on control, but before mouse exits control borders.

sample application attached:
run it, choose "button" at top of scene, choose "DRAGEXITED_TARGET" at right part of scene,
start drag on the button, drag mouse inside of control.
Ubuntu: event handler is called. should not.

same with "DRAGEXITED" event type