A line component will not update if using a cached THREE.Vector3 to call setAttribute. I believe this is because deepEqual is used in component to determine if an attribute was actually updated or not. As such, this probably affects other components that similarly allow (or at least don't explicitly disallow) the use of THREE vectors.

Aside from updating the deepEqual method, another option may be to allow forcing an update via another attribute like needsUpdate.

        init() {
          this.end = new THREE.Vector3();
        },
        
        tick() {
          this.end.set(Math.random(),  Math.random(),  Math.random());
          this.el.setAttribute("line", {end: this.end}); //will not update after the first tick
        }

• A-Frame Version: 0.8.2
• Platform / Device: any
• Reproducible Code Snippet or URL: https://glitch.com/edit/#!/heavenly-piranha