Snapshot backup for netapp luns that on same volume

We are preparing to phase out our NetApp FAS3220 storage and migrating data to other platforms. Currently, we have three LUNs created on the same NetApp volume. These three LUNs are connected to a Windows cluster server and presented as drives D:, E:, and F:. I created an IntelliSnap backup job on the cluster client with block-level backup enabled and included all three drives (D/E/F) in the same backup set. I also configured a proxy computer (same OS version as the file server) for backup copy operations. When running the backup job, the process hangs at the file scan stage: One snapshot is created successfully at the NetApp volume level. Three snapshots with the same prefix (volume snapshot label) are shown as mounted to the proxy in netapp. On the proxy, only two drives appear, and the job remains stuck for more than 6 hours. Troubleshooting Performed: Tested with SnapTest: creating and mounting a snapshot for a single LUN/drive works without issues. When attempting snapshots for all three LUNs together, snapshot creation on NetApp works fine, but the mounting fails/stalls. My suspicion is that because all LUNs reside in the same NetApp volume, the snapshot is mounted for the first drive, but subsequent mounts fail due to LUN/device busy conflicts. Request: Please confirm whether IntelliSnap supports multiple LUNs from the same NetApp volume being included in the same backup set, and if not, provide guidance on the recommended configuration. Additionally, please advise on any workaround or configuration adjustments that would allow us to back up all three LUNs reliably. Checked the event view, the Error code: 17:2/19:122/32:392/32:376 show in event view window.