I've had some Japanese Macaques "escape" on me a few times recently. Even spotted one doing it: they run full pelt towards the inner corner of their L-shaped habitat, and clip straight through the corner. Sort of "quantum tunneling" macaques, they are, but it still counts as "escaped", even though they're just sitting there, quietly, still inside their habitat.
I slapped down some azalea strips to try to make the wall thicker and force them to walk/run all the way around rather than take the handy quantum shortcut, but it still happened once after I did that.