Position of drop down previewing options in Navbar is not correct

The related info:
Drupal core: 7.24
PTP: 7.x-1.0-rc1
Navbar: 7.x-1.0-alpha10

I have tried this combination in two computers (Mac and Ubuntu), but the issue is same, the dropdown menu position is around middle left when I click right top corner icon, and when I move mouse out to choose one breakpoint, the drop down menu disappeared, so I even can not use this module in this way.

I use the backbone 1.0 and underscore 1.4.4 by checking the code. but I see this module use jquery.ui.position, I am lost here, can anybody help?

Thanks in advance.

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Update: Navbar module updated, and the issue has disappeared.