About 9/10 attempts the clock tower ports me back to start for no reason. I’ve had it port me out the moment I got in, in the middle of jumping and while I’m standing waiting for the next part of the stairway to appear. I’ve had it port me out while I’m running up the middle of the steps as well. All without me falling or being anywhere near the green mist.
I also had it bug out and port me to my own instance of the tower where I was alone and no green mist ever spawned.