You restore a backup of a Windows Server 2008. Backup reaches 88% and does not show any progress for a long time.
In logs, you see that the software is performing bootability fix.
A bug in Windows operating system causes an enormously large amount of 'Volume' entries in Windows Registry.
You need to wait until Acronis Backup completes registry check.
Later, if you plan to continue backing up the restored machine, you can apply this fix on it to prevent this issue during a future restore operation.
Alternatively, if the source machine is still available, you can apply this fix on it and then recreate the backup. Recovery from this backup will run much faster.