To reproduce:
1. Create a new Unity project.
2. Add a script to a game object with this code:
void Awake()
{
if (System.Threading.SynchronizationContext.Current != null)
{
Debug.LogError("A default SynchronizationContext is set!");
}
}
3. Build a Windows standalone player (development build)
4. Notice error message
5. Run scene in editor
6. Notice that error doesn't appear