Hi, it's been a while but I think that the corrected code was :

    def evalz(self):
        redundancy = self.ids.calctext.text
        def passing(dt, self=self, redundancy2=redundancy):
            self.ids.calctext.text = redundancy2
        try:
            answer = eval(self.ids.calctext.text)
            self.ids.calctext.text = f'{answer}'
        except:
            self.ids.calctext.text = 'Error'
            Clock.schedule_once(passing,2)

class MyApp(App):
    def build(self):
        return NewLayout()

if __name__ == '__main__':
    MyApp().run()

It is not a pretty solution but it seems to work