I'm playing 0.9.14b "Brains" on a Mac laptop running OSX 10.10.5. I entered an exit portal from... whichever is the second level with a treasure room. Level 5? The game froze and I got the spinny Mac beach ball; had to Force Quit the app.
This could be an OS issue or it could be the game. I had exactly 1 second left on the timer when it froze, though; if I have the patience to try to reproduce it I may attempt to again leave a level at the last second and see if that does anything fishy. (I have successfully exited this level on this build in the past. Maybe even during the last few seconds of the security timer, though perhaps not with exactly 1 second left.)