Is the M: drive the quorom\msdtc? That will get backed up by the system state.

Make sure you are installing into the role that contains the actual data you are backing up.

The cluster name itself is just the cluster db (quorom\msdtc) so the Z: wouldn’t be picked up unless you manually specified it.

If you install to the target role, you gxclusplugin should reside in the same location as the target data with the name\IP.

The job results should also be in this role so it is always available regardless of host.

Make sure the Z: drive is in the role as a disk resource and not just a share.

We ended up finding that the backups jobs were getting redirected to the passive nodes.

We found that if we opened Process Manager on each of the nodes, they all thought they were the active node:
 

Solution : stopped the passive node Commvault services, ran a cluster backup and started the passive node Commvault services,