Just a pure guess, but I think you'll see this issue only during AP previews. It seems like the 7am is lasting a couple of minutes. All the people who weren't able to get a park res to MK just booked another park, so there's most likely way more people trying for 1 then there is 7
I was group 17 this morning, even with the delay, I walked right onto the ride, didn't stop once in the queue (was called at 1030)