Come to find out that adding "onerror" to zombie in the screenrc file does help there is just what is approximately a 10 second delay between the "Command detached from window" message and the upgrade process exiting 0 which then causes screen to disappear.
Come to find out that adding "onerror" to zombie in the screenrc file does help there is just what is approximately a 10 second delay between the "Command detached from window" message and the upgrade process exiting 0 which then causes screen to disappear.