runAnimationGroup causes spinlock #1

I noticed an issue with runAnimationGroup in this particular code example:

https://github.com/ipmcc/SOExamples/blob/master/animation/AnimTextFieldUsingNSAnimationContext/AnimTextField/SOAppDelegate.m

In some versions of OS X animating the NSTextField in quick succession (e.g. clicking on the button in the example rapidly) will create a race condition leading to a spinlock. I noticed this question on stackoverflow that mentioned a similar behavior, although there was never a response. I'm filing this issue in the hope that you are someone may know of a solution to this problem, thanks.