Entry IsVisible Sometime is not working on iOS in XF1.4

        <Entry Placeholder="发动机号" VerticalOptions="Start" HeightRequest="40" Text="{Binding Engineno,Mode=TwoWay}" IsVisible="{Binding Engine}" />
        <Entry Placeholder="车架号" VerticalOptions="Start" HeightRequest="40" Text="{Binding Classano,Mode=TwoWay}" IsVisible="{Binding Classa}" />
        <Entry Placeholder="车辆登记证书号" VerticalOptions="Start" HeightRequest="40" Text="{Binding Registno,Mode=TwoWay}" IsVisible="{Binding Regist}" />

when the value changed It does not be visible in iOS sometimes ,anyone who knows why ,It work fine on Android