It's a Unity bug.
Open SkeletonAnimation.cs
And look for this method:
void Update () {
Update(Time.deltaTime);
}
And add "public" so that you end up with this:
public void Update () {
Update(Time.deltaTime);
}
That should be enough to get UWP to work correctly.
(As you can see, it's a nonsense error. UWP gets confused while other platforms have no problem.)
11 Sep 2017 3:53 pm
Sent a bug report to Unity.
12 Sep 2017 7:36 am
Heard back from their bug report guys. They saw the bug, forwarded to their devs. Now we wait.