Unable to backup to a UNC path with a gMSA I'm trying to automate backups using Ola Hallengren's backup scripts.

I'm testing this out on a SQL express instance 2008 R2 (I know it's EOL today).  I've setup the jobs and I created a scheduled task to run a batch script with SQLCMD.  The scheduled task is running as a gMSA

Everything seems to be groovy except for some darn reason I can't reach the UNC path I'm trying to backup to.  The error I'm getting is as follows:

Msg 50000, Level 16, State 1, Server servername\instancename, Procedure DatabaseBackup, Line 878
The directory \\servername\sharename does not exist.


This has to have something to do with the gMSA not having proper permission to the share or something but I've explicitly granted this account full access at the share and NTFS levels (out of desperation) and still no dice.  Obviously the share does exist, and I can connect to it just fine using other accounts.

If anyone has any experience running SQL server with gMSA's who could shed some light on this I would greatly appreciate it.

Thanks,

UPDATE - Just for kicks I gave the service account sysadmin priviledges on the SQL server and now it works.  I have no idea why that would fix problems with access to a file share so the error is definitley misleading.  What are the minimum rights required to run a backup for databases?  Initially I gave the service account the "public" server role and "db_backupoperator" on each database.  Looks like I'll need more than that?  The target here is least priviledge.

Thanks
If you check the documentation for Ola Hallengren's solution, you'll see under "Which permissions are needed for the SQL Server Maintenance Solution to work?" the following:


  
  DatabaseBackup: sysadmin
  DatabaseIntegrityCheck: EXECUTE on dbo.DatabaseIntegrityCheck, VIEW DEFINITION on dbo.CommandExecute, VIEW DEFINITION on dbo.CommandLog, VIEW SERVER STATE, db_owner on all target databases
  IndexOptimize: EXECUTE on dbo.IndexOptimize, VIEW DEFINITION on dbo.CommandExecute, VIEW DEFINITION on dbo.CommandLog, VIEW SERVER STATE, db_owner on all target databases
  


I believe the reason sysadmin is required is because the solution uses xp_fileexist to check the existence of a directory, and this extended stored procedure requires sysadmin rights.

Normally, the jobs are executed by a SQL Agent which has sysadmin rights by default granted to the per-service sid NT SERVICE\SQLServerAgent (or NT SERVICE\SQLAgent$instance_name for a named instance). If you use a proxy to run the jobs in SQL Agent, that proxy also needs sysadmin, as does the user account running the procedure from any other scheduler, as is your described scenario.