MvvmCross: MvxCommand(async () => await ...) blocking UI

I have a ViewModel with the following code

 public IMvxCommand LoginCommand => new MvxCommand(async () => await LoginClicked());

 private async Task LoginClicked()
 {
     //.....
 }

Which has a couple of seconds (depending on how old the device is) delay once I click on the button, ultimately blocking the UI. (I have tried the above written in multiple ways).

However when I change the code to the following, then there are absolutely no delays.

public IMvxCommand LoginCommand => new MvxCommand(LoginClicked);

private void LoginClicked()
{
    Task.Run(async () => await Login());
}

Obviously I prefer the above option, but it causes bad user experience. I have only had the option to try this on Xamarin.Android so far, will shortly test it on iOS and WP.

using

1. MVVMCross 4.0.0-beta7
2. Latest Xamarin
3. VS2015.1
4. Android 5.1