Inconsistent behavior after using collapse('show') on Accordion

Created by: davidtgq

http://codepen.io/anon/pen/zoNyvO?editors=1010#0

To reproduce the problem:

1. Open Item #2. It automatically collapses Item #1.
2. Open Item #1 again. Item #2 does not automatically collapse.

The above steps can be also reproduced substituting Item 3 in lieu of Item 2 to demonstrate the same problem where Item 3 stays open.

The problem does not exhibit when:

• using .in instead of collapse('show')

• collapse('show') is removed such that the page loads with all items collapsed