VMware-Snapshot is not deleted after Netapp-Snapshot (by SnapCenter)

Environment:

vCenter 6.5

SnapCenter Server 4.1.0.1664

SnapCenter Plug-in vsphere 4.1.0.1664

Snapshots are triggered by SnapCenter and “VM Consistency” is set to true

Behavior:
We have one Resource Group for each datastore. In each datastore are several VMs with vmdks (~30-40). For some Resource Groups the backup job works as expected:

1. VM Snaps are generated (takes 1-2 minutes)
2. NetApp Snap is generates (takes seconds)
3. VM Snaps are removed (takes 1-2 minutes)

Everything fine!

Issue:

For some other Resource Groups step

1. takes a bit longer (~5-10 Minutes)
2. works as expected
3. does not work at all – no VM Snap is removed – and that’s the major problem

It seems related to the fact, that within the appropriate datastore one or more machines cannot be quiesced.

Workaround: Disable “VM consistency” – but this is not a solution.

Any ideas how to troubleshoot?

Is any of the timeouts here helpful?

https://library.netapp.com/ecm/ecm_get_file/ECMLP2840884 p. 82

Thank you in advance!