Default Constructor error on apple devices

After moving to 1.4.0, in Visual Studio debugging against iPhone I will sometimes get this error, on the Mac using Xamarin Studio I get this error every time.
"Default Constructor not found for type MyApp.Renderers.MyWebView"
If I change to iPhoneSimulator the error does not occur using either environment.
For devices I'm using an iPod running 8.1 and an iPad running 8.2 My simulated devices are running 8.2