Commvault MS SQL plug-in user permission / role

Hi everyone,

I'm working on a custom set of permissions for our MSSQL admins to allow them to perform on-demand backups. Despite granting what I believe to be more than sufficient privileges, they are still encountering errors.
The process works perfectly when the user has master rights.

Current permissions:
 

Error with those:

 

Has anyone successfully configured a least-privilege role for this scenario and could share?