ShadowProtect continuous incrementals - every so often, it wants to do a full backup and it fails

I have a bunch of machines running shadowprotect continuous incrementals with no problems, except for 1 machine.

This is v5.2.3 (the most up to date for v5).

It's at a remote location with a VPN back to a NAS device in the main office.  It does a continuous incremental fine on the 3x a day schedule most all of the time, then the logs show that it tries doing full backups on the  weekends (3 times a day), fails within 2 seconds of starting with things like:

05-Oct-2015 06:30:00      service      509      Cannot get access to destination object
05-Oct-2015 06:30:00      service      101      Cannot execute job (The network path was not found. 0x80070035(2147942453))
05-Oct-2015 06:30:02      service      510      Failed to send email notification to ____@_____.com. ChilkatLog:
...
05-Oct-2015 06:30:02      service      510          Failed.

the failures / full backups (they go hand in hand) seem to be on the weekends only.  theres another machine in that remote office, also backing up over the VPN. No failures, no attempts to do fulls, same schedule (actually 1/2 hour later so they both don't use the VPN at the same time).  so the VPN is up all the time, the NAS is up all the time.

Any thoughts on why the backups on the weekend fail immediately on this machine only and that the backups on the weekends try to be full, even though the the 1 backup job is set for continuous incrementals?
 
Also, in this machine's backup history, the entry for each of the failed backups has the target as \\backupnas\machineA\machineA C_Vol  (no numbers after it).

The successful continuous entries show the target as \\backupnas\machineA\machineA C_vol-B001-i09xx.spi

Shouldn't the full job be trying to make a .spf?  And the backup would get a number b002?  Those are NOT noted in the target name for any of these failed fulls.

Thanks!
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noxchoGlobal Support CoordinatorCommented:
Is there any other tasks running on this machine at the time when backup tries to take full and fail?
I can explain why it tries to take full. Usually it will check the previous creation of full and incrementals. Now imagine, the machine does not have access to a storage and thus checking the previous full or increment is impossible. What is a logical behavior of backup tool?
Correct - it must create full image first because it did not find it on your NAS (due to network connection, or NAS rejected the connection etc etc). And it thinks that none of such image was previously created or they were deleted. We need new full!
So to narrow your problem to its bottleneck I would suggest you editing the existing backup job and letting it do backup to locally connected drive. For example USB drive and see if you are able to reproduce the problem. I guess you will not be able to reproduce it this way.
So check more carefully the network. Maybe the NAS is reaching the maximum number of open threads allowed per time? Or it is going to maintenance?
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