Acronis backup for Vmware error "failed to close raw hard disk data file"

Hi, I've and appliance backing up 3 vm. Since 2-3 days i receive this warning after backup completed in all 3 virtual machines. Tried to reinstall appliance (because rebooting didn't solve) but errors remains.

Some Help? thank you.

Failed to close raw hard disk data file '[Datastore_NAS] SRV01/SRV01-000003.vmdk'.
Additional info: 
--------------------
Error code: 95
Module: 83
LineInfo: 1b5da992938b2afe
Fields: 
Message: Failed to close raw hard disk data file '[Datastore_NAS] SRV01/SRV01-000003.vmdk'.