I don't think it's a bug, it's just the way the app is. We can handle it by using something like:
`self.wait_for_condition(lambda m: m.find_element(*self._wifi_data_locator).text == u'0.00 B', message='Wifi usage did not re-set back to 0.00B')`
Which would replace the sleep and also make the assert on line 138 redundant.