Help! Problems with Unicorn Hat, Scratch Gpio7 on Raspberry Pi 3

[Ferlin]

I just bought the Unicorn Hat to design a workshop station for kids with scratch. The problem is. The first orders in Scratch with the Unicorn Hag work but then it just doesn't react anymore and the colors freeze. The only thing I can do is restart scratch. But like this it is really frustrating . I need to present the station next week. Is there a solution or do I have to resell it ?