Clicking "Decline" declines and then merges a pull request

On a number of occasions in the past few weeks, I have attempted to decline pull requests, only to find out later than I had declined and then merged them.

Most of the time, I see this:

1. I click the "Decline" button.
2. I'm given the popup error informing me that my information is out-of-date.
3. I refresh the page.
4. I click "Decline" and close the tab or navigate away.

Most recently, I did not receive the error popup, and so I did not realize that the merge had occurred until I later ran a git log myself.

When I visit the pull request page again, I see records indicating that I declined and then merged the pull request. This is particularly odd since a merge cannot be performed on a declined request.

I am using Google Chrome 32.0.1700.77 on OS X Mavericks (10.9.1). I am one of the few people at work using Chrome on a Mac to go through pull requests (most are on Linux), and to my knowledge, I am the only person who has experienced this.

I realize that this isn't much information to go on; I'll happily provide more if given guidance as to what information I can collect by myself or via our administrators.