External item dragging into scheduler

Hi,
We have used makeDraggable function and set keepElement: true as we have to use same item multiple rows.
When i dragged the same item twice and moved or resized the item.One item disappears.
Please help on this.

function makeDraggable() {
var parent = document.getElementById("external");
var items = parent.getElementsByTagName("li");
for (var i = 0; i < items.length; i++) {
var e = items[i];
var item = {
element: e,
id: e.getAttribute("data-id"),
text: e.innerText,
duration: e.getAttribute("data-duration"),
keepElement: true
};
DayPilot.Scheduler.makeDraggable(item);
};
};