What type of backup are you running? File, Image, etc.?
I have done some research and see a similar issue reported by a customer in version 7.2.1.49 with a fix scheduled for the next patch release. I don't have a date but it will likely be around November 9th or 10th. I would recommend you open a support case to verify if it's the same issue and if Support has a work-around or if a pre-release agent is available for testing.