monogame corrupts xamarain.forms display (text label, button...)

Hi there, I'm using xamarin.forms with monogame on android for a game.
I use xamarin.forms for parameters, highscore(MainActivity)... and when I need to launch the game itself, I start monogame in a GameActivity.
It works fine, the problem is when I need to leave the game to go back to xamarin.forms.
In the monogame part, when I leave, I do Game.Activity.Finish();
then it goes back to the MainActivity having my xamarin.forms panel. but then the text in label, button, are corrupt (showing black square instead of text).
any idea of whats going wrong?
thanks in advance.