Mongo::Auth::Unauthorized: User ... is not authorized to access ...

Dear All,

We keep getting the following error when upgrading mongo gem from 2.4.3 to 2.5.3 and 2.6.2.
Rolling back the driver to 2.4.3 worked without problem.

Mongo::Auth::Unauthorized: User ... is not authorized to access ...

The errors seem to occur intermittently.

We are using Mongoid with the following options:

• database
• hosts
• options
  • user:
  • password:
  • auth_mech:
  • read:
    • mode:
  • replica_set:
  • connect: :replicaset

The supported mechanisms in our MongoDB are "MONGODB-CR", "MONGODB-X509", and "SCRAM-SHA-1"

Any help would be greatly appreciated.
Thank you.