If you upgraded from Rebit 3 to Rebit 5, we have seen Rebit have difficulty converting the old backups to the new ones if the indexes are corrupted on the drive. Index corruptions occur when the drive loses power unexpectedly or is not Safely Disconnected before being unplugged. Once they happen, Rebit will get stuck trying to convert these recovery points to no avail. The easiest solution is to format the drive and set is as a new backup location. If you do not want to lose the old Rebit data, you can also use a different external drive for backup.