In v15 SP5, under Backup and Restore > Backup Schedule, if you use the buttons to change Configure backup rotation, the value is not saved when you click OK. You may think you have increased the value from 1 to 7 or 14, but you have not. I only discovered this after almost two weeks of missing backups. If you manually type the Configure backup rotation value that you want, it will be saved when you click OK. Re-open the Backup Schedule window to double-check. Update It seems this is an issue with Firefox (version 52.0). If you use the spinner in Chrome (version 57.0.2987.110), the value "sticks" when you click OK.