Netbackup jobs waiting for a tape drive but there are tape drives available

Netbackup is version 9.1.0.1 on a windows 2012R2 server.  Have a quantum i500 library with 6 LTO6 drives.

So this environment was inherited as I wasnt the original person setting it up.  Im wondering if there is a setting regarding what Im seeing.  Basically when our evening daily jobs kick off I notice and still noticing hours after the jobs start that only 3 of the 6 drives are actually being used.  Im seeing the following verbiage in a current job that is in the activity monitor waiting for a drive.

Mar 14, 2023 7:00:00 PM - Info nbjm (pid=10604) starting backup job (jobid=1002038) for client s01-prelimg-1a.*****.com, policy Windows-s01-prod, schedule Incremental
Mar 14, 2023 7:00:00 PM - Info nbjm (pid=10604) requesting STANDARD_RESOURCE resources from RB for backup job (jobid=1002038, request id:{96626213-4D54-44B9-93C8-43FB8F85B4F7})
Mar 14, 2023 7:00:00 PM - requesting resource  backup-1-hcart3-robot-tld-0
Mar 14, 2023 7:00:00 PM - requesting resource  backup-1.*****.com.NBU_CLIENT.MAXJOBS.s01-prelimg-1a.*****.com
Mar 14, 2023 7:00:00 PM - requesting resource backup-1.****.com.NBU_POLICY.MAXJOBS.Windows-s01-prod
Mar 14, 2023 7:00:05 PM - awaiting resource backup-1-hcart3-robot-tld-0. Waiting for resources. 
          Reason: Maximum partially full volumes has been reached, Media server: backup-1.*****.com, 
          Robot Type(Number): TLD(0), Media ID: N/A, Drive Name: N/A, 
          Volume Pool: Systems, Storage Unit: backup-1-hcart3-robot-tld-0, Drive Scan Host: N/A, 
          Disk Pool: N/A, Disk Volume: N/A 

Under Netbackup Management in the admin console under Storage units the library backup-1-hcart3-robot-tld-0 has Maximum concurrent write drives set to 6 which is the total amount of drives we have.

Is there a setting for a limit on ACTIVE jobs running which will make other jobs wait even though there are free drives available.  

Would this have to do with the volume pool setting "Maximum number of partially full media"?

Thanks

BC