Safepoint backup was successful, but now fails

I have two My Book Live network drives connected to my home network (Windows 10). The first My Book Live drive (Name: NetworkDrive) contains all my data, music, pictures, documents, etc. The second My Book Live drive (Name: BackupDrive) contains my new SafePoint. (A backup copy of everything on the first My Book Live.)
The safepoint backs up every night.
In the beginning, the safepoint backup was “Successful” every night. Lately, however, I get the following unsuccessful message:

Following events are generated on your MyBookLive NetworkDrive.

Event title:There was an error updating your safepoint.

Event description:2 - There was an error updating your safepoint BackupOfAllData on the Public share on BACKUPDRIVE.

Severity:warn
Event code:1102
Event time:03-07-2016 11:04:01 PM

Firmware version: 02.43.10-048

What might cause my SafePoint to suddenly become unsuccessful when backing up?

Hi there,

Does the safepoint fail on a specific file or percentage? have you changed any setting on the drive or the network lately?

ArMak,

I have not made any changes on either of the two drives. The only change
was months ago when the firmware was updated.

Thanks.