Unbuyin is no longer working in the latest build. I figure it's related to the change in how you implemented manual seating.
I consider this issue high priority. Please let me know as soon as fix is available. Sorry I didn't notice it before release of build #6.
Looks like if you assign at least one seat manually, the unbuyin button becomes enabled. Should be an easy/quick fix, but in the interim, assigning at least one seat manually appears to be the workaround. Let me know if you find this not to work. I only did a very quick test, so I might have missed something.