Different performance on multiple of the same device?

So I have made a wheel that you touch and drag to spin in ionic as a navigation system. I have tested it on my iPad Air 2, iPhone 6s and Nexus 6p. All of them work great, however I sent out a test build and for the users testing the wheel often does not recognize the touches, or stutters depending on how hard you touch. As in if they touch very lightly the wheel spins well, if they push down it causes issues. The weird part is I have tested it on 4 iPhone 6s Plus devices, and 2 of them work and 2 of them don’t. So then maybe it has to do with how many apps are open? storage on the device? iOS version? I have no idea. Here is the relevant code

         drag = $ionicGesture.on('drag', function(e){

            var pageX = e.gesture.center.pageX;
            var pageY = e.gesture.center.pageY;

            currentAngle = getAngle(pageX, pageY) - updatedAngle + originalAngle;
            absoluteAngle = getAngle(pageX, pageY);
            circle.style.transform = circle.style.webkitTransform  = 'rotate(' + currentAngle + 'deg)';

            for (var i = 0; i < circles.length; i++) {
              circles[i].style.transform = circles[i].style.webkitTransform = 'rotate(' + -currentAngle + 'deg)';

          }, angular.element(circle));

Like I said this is working great on all the devices I have. Is there a way to limit the cpu usage of a simulator so I could test? Any ideas would be awesome