AD Sync task stopped working SGN 8.00.2.16 'Failure (805306375)'

Question

SGN 8.00.2.16

I followed the KBs to get the scheduled sync tasks working, giving the AD user rights to read the various parts of the domain, write to the database, write to the synclog.csv, etc., and it was all working and my hourly sync jobs were all succeeding.

Now they all say 'Failure (805306375)' and when I try to manually sync it says "The directory is being synchronized by "AdminMSO". Please try again later." where I am of course AdminMSO.

I've rechecked all permissions on the account, restarted all of the SGN services, rebooted the server, recreated the sync.

Every hour the log file looks like this:

8/22/2017 7:00:12 PM Synchronize all imported containers startet. Success
8/22/2017 7:00:12 PM Synchronization startet. Success
8/22/2017 7:00:12 PM The container: CN=Poa Groups,DC=<POA> will not be synchronized. Success
8/22/2017 7:00:12 PM The container: CN=Poa Users,DC=<POA> will not be synchronized. Success
8/22/2017 7:00:12 PM The container: DC=<POA> will not be synchronized. Success
8/22/2017 7:00:12 PM The directory will be synchronized by an other user, please try again later Failure

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james63 · Accepted Answer

And almost immediately after posting I just figured out what to do about it. Tools > Options > Directory tab, there is a 'Reset import flag' button. It said that the last job was 5 days ago and asked if I wanted to cancel it. 
 An arbitrary job and my hourly job just ticked over and say Success. 
 Sophos can I recommend setting the Sync job or script to cancel its self if it finds a single job in a failure state for 5 days the way you can set the Windows task scheduler to cancel jobs that run too long? 
 
 Edit- or if that's too much then add an option to the built-in scheduler to set up email alerts on a job?