When attempting to backup Exchange 2007 resources configured with either Local Continuous Replication (LCR) or Cluster Continuous Replication (CCR), the backup job will intermittently fail with 0xe000fedd, 0xe000037b, 0xe00084af or 0xe000846b errors
I did a lot of research on this issue. different structures, but not everyone. The real solution is correct in this article
Look this a my solution
Except we already say set it to "Active Copy Only" and your referenced article mixes up versions of BE and is confusing as to what you have actually done.
We also know that the Microsoft Hotfix that allegedly fixed the issue to allow a backup from the passive Copy does not work for 100% of environments that had the problem - hence we have not said fixed and to be honest I doubt it will be now as Exchange 2007 is not the current version and Exchnage 2010 does not have the problem.