title: Tkinter scrollbar scrolling infinitely down but breaks when scrolling up
body: <p>Hi I can't seem to find the cause of a weird issue I am having in Tkinter\Python</p>
  
  <p>When using the following code to create a scrolling window on a canvas</p>
  
  <pre><code>myFrame = Frame(ob)
  ob.create_window((0, 0), window=myFrame, anchor='nw')
  scroll = Scrollbar(sub, orient="vertical", command=ob.yview)
  ob.configure(yscrollcommand=scroll.set)
  scroll.grid(row=0, column=1,  sticky=N+S)
  # add check boxes for clients to buttons
  for row in clients:
      v = IntVar()
      item = Checkbutton(myFrame, text=row[1], variable=v)
      item.va = v
      item.grid(sticky='w')
      clientlist[str(row[0])] = v
  ob.configure(scrollregion=ob.bbox('all'))
  </code></pre>
  
  <p>It creates the windows inside of the canvas and also creates the items inside of it. It even creates the scrollbar next to the canvas just fine.</p>
  
  <p>The issue is that when I scroll down it allows me to scroll forever. It also scrolls upwards just past the top most item in the canvas window and then disables the scroll function.</p>
  
  <p>Any insight on this as it seems I must not be setting the scroll region correctly is my guess but I am not sure what is wrong with it.</p>