A problem with DragBehavior

draglabel.kv

#:kivy 1.0.9

<DragLabel>:
    # Define the properties for the DragLabel
    drag_rectangle: self.x, self.y, self.width, self.height
    drag_timeout: 10000000
    drag_distance: 0
    border_width: 2
    font_size: "20dp"
    text: ""
    color: 1,0,0,1
    size_hint: None,None
    size: self.texture_size[0]+2*self.border_width,self.texture_size[1]+2*self.border_width
    canvas.before:
        Color:
            rgb: 0,0,0
        Rectangle:
            pos: root.pos
            size: root.size
        Color:
            rgb: 1,1,1
        Rectangle:
            pos: root.x+root.border_width,root.y+root.border_width
            size: root.width-2*root.border_width,root.height-2*root.border_width
        Color:
            rgb: 0,0,0

FloatLayout:
    # Define the root widget
    DragLabel:
        # size_hint: 0.25, 0.2
        pos: root.width/2-self.width/2,root.height/2-self.height/2
        text: 'Drag me'
        color: 1,0,0,1
    DragLabel:
        pos: root.width/2-self.width/2,root.height/2-self.height/2
        font_size: "23dp"
        text: 'Drag me over or under?'
        color: 0,1,0,1

main.py

from kivy.uix.label import Label
from kivy.app import App
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.gridlayout import GridLayout
from kivy.uix.behaviors import DragBehavior
from kivy.lang import Builder
from kivy.core.window import Window
Window.clearcolor = (1, 1, 1, 1)

class ZDrag(DragBehavior):
    def on_touch_down(self, touch):
        parent = self.parent
        if not hasattr(parent,'allow_more_drags'): parent.allow_more_drags = True
        if parent.allow_more_drags:
            success = super(ZDrag, self).on_touch_down(touch)
            if success:
                parent.allow_more_drags = False
                parent.remove_widget(self)
                parent.add_widget(self)
            return success 
        return False
    def on_touch_up(self, touch):
        if self._drag_touch and self in [x() for x in touch.grab_list]:
            self.parent.allow_more_drags = True
        return super(ZDrag, self).on_touch_down(touch)
        
        
class DragLabel(ZDrag, Label):
    pass

class DragLabelApp(App):
    pass


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

Here is the fix:
def on_touch_up(self, touch): if self._drag_touch and self in [x() for x in touch.grab_list]: self.parent.allow_more_drags = True return super(ZDrag, self).on_touch_up(touch)

You had set return super(ZDrag, self).on_touch_up(touch) to return super(ZDrag, self).on_touch_down(touch)