ACTUALLY IF THE CODE FAILS WITH Maximum call stack size exceeded SUBSEQUENTasserts are wrong

Challenge http://www.freecodecamp.com/challenges/bonfire-no-repeats-please has an issue. Please describe how to reproduce it, and include links to screen shots if possible.

function permAlone(str) {
doPerm(str, []);
return permutations.filter(function (str) {
var repeats = /(.)\1/;
return !repeats.test(str);
}).length;
}
var permutations = [];
function doPerm(str, arr) {
if (typeof (str) == 'string') str = str.split('');
if (str.length === 0) permutations.push(arr.join(''));
for (var i = 0; i < str.length; i++) {
var x = str.splice(i, 1);
arr.push(x);
doPerm(str, arr);
arr.pop();
str.splice(i, 0, x);
}
}
permAlone('aba');

expect(permAlone('zzzzzzzz')).to.equal(0);Maximum call stack size exceeded ???

After first error the subsequent assert calls return correct number + response from the above code
above code returns 2 (CORRECT)

expect(permAlone('aabb')).to.equal(8); will return 8 + 2
Code run alone for 'aabb' will return 8 though...

expect(permAlone('aab')).to.be.a.number;
expect(permAlone('aab')).to.equal(2);
expect(permAlone('aaa')).to.equal(0);
expect(permAlone('aabb')).to.equal(8);
expect(permAlone('abcdefa')).to.equal(3600);
expect(permAlone('abfdefa')).to.equal(2640);