if you are trying to migrate resources from one subscription to another and if the resources have Azure VMs which are getting backed-up by Azure Backup, You may encounter an issue related to restore points even after you stop the Azure backup and dont include backup vault for the migration 

Resource:’
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/AzureBackup_20190110_121719′, Code:InternalDiskRestorePointError, Message:An internal disk management error occurred.; Resource:’XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/AzureBackup_20190107_121358′, Code:InternalDiskRestorePointError, Message:An internal disk management error occurred.; Resource:’
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX/AzureBackup_20190109_121226′, Code:InternalDiskRestorePointError, Message:An internal disk management error occurred.

If you try to manually delete the restore points from the Azure portal, you will see it keeps on showing as deleting for hours and never confirms

PowerShell Command to delete restore points – Replace the restore point’s Resource ID to delete it using the powershell

Remove-AzureRmResource -ResourceId “Add Resource ID Here” -Force

You may need to run this command multiple times to delete the restore point. Microsoft has confirmed that this issue is a bug and will need multiple retries to delete a restore point using the powershell

Cheers!!