@Tore, the event is a typical error when a snapshot commit lead into a cluster failover and the database log can not be truncated. As the Truncation is replicated through the cluster, it could happen that one of the other dag database backups where successfull and truncation is replicated. You need to look why the Snapshot truncation lead into clutser failovers. Did you had set the correct cluster props?
Please look up the error code in my blog entry. You will find a lot of tips how to address this and why this happens.
http://andyandthevms.com/exchange-dag-v ... plication/