Upgrade to 7.5 - Unable to take backup

Upgrade to 7.5 - Unable to take backup

Having a problem doing a test upgrade of 7022 to 7.5

When I start the process using updateManager it attempts to take the backup as it normally does, but them fails stating it has a problem taking the back. Hence not proceeding.

System is shutdown.
I've taken backups using Backupdata twice now and these have worked.

The system is a clean 7022 build with our live data then restored to it and checked to see it is operating in 7022 environment.

What log file do I need to be looking at to determine the cause of this issue and ultimately move on with the 7.5 testing prior to go live.

Kind Regards,
Andy