A little more technical detail on what we're seeing:
The X/T activity is based on an audience where the value of an mbox parameter is set to 'n' and, for test purposes, the current page URL contains admin=9.
If you go to the page (let's say X.html?admin=9) and have the parameter set to 'n' you will properly be put into the activity and see the experience. So far, so good.
Now, you go off and do something so that when you come back to the page, the parameter is now set to 'y'. I would not expect to still see the experience, but just the default page. However, I still see it.
Similarly, if I just change the URL of the page to X.html?admin=1, I still see the experience. Given the audience says to look for admin=9, I would not expect to see the experience from this activity.
It just seems like once somebody enters that activity, it keeps showing it to them regardless of whether they still match that Audience which doesn't sound like it should be the case. So we aren't sure if this is a bug, we are misunderstanding how this should work or if there is some setting that isn't set right.