I just selected this STF and as soon as the team had all warped in we got the popup saying Leave Map and that was it. We didn't get to do anything, (we all had to leave the map). The STF is on the cool down timer now.
I had no problems when I took part in this particular STF earlier today before the patch.
this has been an ongoing problem for quite some time. What you described happens when the run gets completed but the "leave Map" trigger doesn't get activated (lets call it a trigger for simplicities sake). Then the people who just did that run get all impatient and leave creating open slots in an active run. The open slots get filled from the queue, and essentially screw over the joining players due to the run being complete. Of course this problem has been brought up often, and ignored just as often.