I'm currently working on a first person 3D game in javascript using Three.js. I'm using PointerLockControls to control camera movement, and for some reason, the camera seems to be jumping around randomly on the Y axis. It's not noticable in the game itself but if I print out camera.position in my render loop, it changes sporadically. I'm using WASD to call controls.moveForward() and controls.moveRight() which shouldn't affect Y position (I think, correct me if I'm wrong) but it changes nonetheless. This is the code of interest:

var controls = new THREE.PointerLockControls(camera, document.body);
document.onclick = function () {
    controls.lock();
}

function loop() {
            if (wDown) {
                controls.moveForward(0.1);
            }
            if (sDown) {
                controls.moveForward(-0.1);
            }
            if (dDown) {
                controls.moveRight(0.1);
            }
            if (aDown) {
                controls.moveRight(-0.1);
            }
            // printing out camera position
            console.log(camera.position);
            renderer.render(scene, camera);
            requestAnimationFrame(loop);
}

Edit: I should note, the Y position only changes when I move using WASD.