Sorry, this looks like another bug caused by the PR for gamepads we released last week.
You should be able to patch the behaviour back to the old version by adding this script to your projects
pc.GamePads.prototype.update = function (dt) {
var pads = this.poll();
var i, len = pads.length;
for (i = 0; i < len; i++) {
this.previous[i] = this.current[i];
this.current[i] = pads[i];
}
};