ScreenUpdating not working properly

Hi all, my problem isn't a major one but it is a curious one. I've been working on an automating data transfers and was told to use this code to stop the risk of siezure:

Application.ScreenUpdating = False
  Code
Application.ScreenUpdating = True

It has worked great for me but today I opened the workbook and the jumping screens are back. Not for every Sub but only for one, even though it has the ScreenUpdating code.

I've uploaded the workbook. The problem is located in Module2 Sub "SourceTransfer"
Can someone run this and let me know if it is an Excel bug or if I have done something wrong?
To run it, copy the data from Sheet1 and paste it into cell B2 of Insert sheet.

Thank you.