Xamarin Forms Crashing System.Reflection.TargetInvocationException

Hello, I'm currently having an issue while launching a xamarin forms app which constantly crashes with this error:

FATAL UNHANDLED EXCEPTION: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.InvalidCastException: Specified cast is not valid.

I've managed to pin point that the error occurs while trying to get the Android Custom Font. (On Platform Android)

    <On Platform="Android" Value="CenturyGothic.ttf#Century-Gothic-Regular"/>

I had not made any changes to the app source code for a while but have recently upgraded to VS 15.7

I've tried deleteing the obj and bin folders in PCL and Android, Clean, Build, Deploy but still have the same issue

I've deleted the font TTF in the Android project and re added making sure that the properties for the TTF are AndroidAsset. With once again a clean and build, deploy and again same error.

I tried a File -> New project which creates a xamarin forms 3.0 app, copied the code over for a test and it works. We are currently using XF 2.4.0

I've also come accross this error

[global::System.CodeDom.Compiler.GeneratedCodeAttribute("Xamarin.Forms.Build.Tasks.XamlG", "0.0.0.0")]
private void InitializeComponent() {
global::Xamarin.Forms.Xaml.Extensions.LoadFromXaml(this, typeof(MainPage));
}

Any suggestions, Thank you.