Surebackup fails after upgrade to V6

[cliffm]

I have had a surebackup job running perfectly on a V5 of Veeam backup and replication.
This network is not on the Internet and the V5 has happily been working perfectly for well over a year now.
If something works leave it alone? I ignored this and upgraded to V6 and then to V6.1.0.204.
Backups are still running OK but surebackup jobs linked to these backup sets via an application group fail.
I get the message "application group failed to start".
I tried reconfiguring the virtual lab (success) and reconfiguring the application group; the application group points to the latest backup.
Is this because the backup sets are split over 2 different versions of Veeam?
I don't want to delete backups.
Will this go away when all backup sets are written by V6?
Will this go away if I do a full backup?
If I can't get the application group to start, does this mean that my backups are suspect?
I have not contacted support yet, thought I might fly this one in the forum.
Any ideas would be much appreciated. Thanks

[cliffm]

Well... This has suddenly started working again.
I guess the last backup that ran this morning fixed the issue.
Surebackup is now able to complete from the current backup sets.