async/await in Windows10 universal app

Hi,

I'm using async/await in a Hololens application, however after await operations I consistently see the error message:

 ToString can only be called from the main thread.
 Constructors and field initializers will be executed from the loading thread when loading a scene.
 Don't use this function in the constructor or field initializers, instead move initialization code to the Awake or Start function.

It doesn't matter what I am doing, or if the Async task even does any work. Does anyone else have any experience with this, any suggested workarounds?

The code is simply as follows

 public class TestAsync : MonoBehaviour {
 // Use this for initialization
 void Start () {
     TestAsyncFunc();
 }

 // Update is called once per frame
 int count = 0;
 void Update () {
     float sinScale = (float)Math.Sin(0.5f * Time.time);
     transform.localScale = new UnityEngine.Vector3(sinScale, sinScale, 1.0f);
     Debug.Log("Update: " + count++);
 }

 private async Task TestAsyncFunc()
 {
     await System.Threading.Tasks.Task.Delay(TimeSpan.FromSeconds(5));
 }
 }

Setup a hololens scene (using Holotoolkit-Unity), put this script on an object and put a breakpoint at the end of TestAsyncFunc. The system will print the warning message just before breaking.

While I guess this message is harmless, it could hide much deeper issues (I use await quite a bit) and can cause a lot of lost time in debugging!