Reports

self.viewclass = 'Label'

self.layout_manager = RecycleBoxLayout(
    orientation='vertical',
    default_size=(None, 56),
    default_size_hint=(1, None),
    size_hint_y=None
)
self.add_widget(self.layout_manager)

But it is wrong

Correctly

self.layout_manager = RecycleBoxLayout(
    orientation='vertical',
    default_size=(None, 56),
    default_size_hint=(1, None),
    size_hint_y=None
)

self.add_widget(self.layout_manager) 
self.viewclass = 'Label'        # after add_widget

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