After some searching and working, I found the culprit to be Volume Shadow Copy (see reference here). What is odd is that the System Restore was disabled.
When you use FastBack Manager, by default, the VSS service enabled. The VSS service signals the writer applications to stop operation and to start a backup.
This feature is enabled by default , but it may need to be disabled if data managed by some critical applications would be affected by the use of Volume Shadow Copy. The feature can be temporarily disabled by clicking the Advanced button in the Backup U