Hello . The button is called differently but you can make the application do the same operation if you go Settings > Application > Synchronize Repository. After that Backup will "learn" what's really there in the storage and upload whatever is missing at next backup run.

If the discrepancy persists or occurs again, please contact supportatcloudberrylabdotcom

Also, let me remind you to restore your backups for testing before you actually need to restore them to recover from a data loss. A little paranoia is a good thing in this case