Vodafone has a data network reliability of only 75% in Hull, meaning 1 in 4 app, email or web page download requests will fail.
For comparison Three had 97.3% app, email or web page download success.
You have to worry as Cornerstone has been running for quite a while already, things really shouldn't be that bad on Vodafone that you're getting a 1 in 4 failure rate over all those tests in so many locations.