An error message that can be seen while browsing files of a Linux backup (Recover Single File from Virtual Disk):
The ext partition in the selected image disk is not 100% consistent and it may not be browsable.
Please enable the quiesce option for the backup to generate consistent disk images.
When a backup of a running Linux virtual machine is done the guest OS has set a flag on the disk as if the machine was not shut down properly.
Because of this flag you get the warning.
This problem is not solvable at the moment but it doesn't compromise the integrity your backup.
You still can recover the file.