Avamar Hyper-V backups fail with "Error <43426>: Checkpoint creation for Virtual machine '' has failed and will be skipped from backup"

Avamar Hyper-V backups fail or complete with exceptions. All VMs from a specific Hyper-V Node are excluded from the backup with the error: "Error <43426>: Checkpoint creation for Virtual machine '<VM_NAME><VM GUID>' has failed and will be skipped from backup.

The relevant portion from the backup log:

avhypervvss Error <43426>: Checkpoint creation for Virtual machine '<VM_NAME_1><VM_GUID_1>' has failed and will be skipped from backup. For details, please check 'winclustersvc.log'.
avhypervvss Error <43426>: Checkpoint creation for Virtual machine '<VM_NAME_2><VM_GUID_2>' has failed and will be skipped from backup. For details, please check 'winclustersvc.log'.
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avhypervvss Error <43426>: Checkpoint creation for Virtual machine '<VM_NAME_X><VM_GUID_X>' has failed and will be skipped from backup. For details, please check 'winclustersvc.log'.
avhypervvss Info <0000>: --------------------Start [EMC Avamar Plug-in Service for Windows] log ----------

The corresponding portion of winclustersvc.log is located in C:\Program Files\avs\var\ folder on the owner of "EMC Avamar backup cluster client for <Avamar_clustered_client_name>". This can be determined from the Failover Cluster Manager. 

For these messages to show, debug must be enabled on the client in winclustersvc. The "Additional Info" section of this article explains how to enable debug.

winclustersvc WARN<0000>:  WMI API returned error: 'Failed to create checkpoint on collection 'AvamarBackup_<Hyper-V_Node_Name>-app-<#######>' (<GROUP_GUID>).
The operation failed.
Guest cluster validation on VM group 'AvamarBackup_<Hyper-V_Node_Name>-app-<#######>' (<GROUP_GUID>) failed for checkpoint creation.
Size of the VM group 'AvamarBackup_<Hyper-V_Node_Name>-app-<#######>' (<GROUP_GUID>) is not same with the size of the guest cluster.'  
winclustersvc DEBUG<0000>: <=== ValidateOutput  
winclustersvc DEBUG<0000>: Retry '1', WMI API 'CreateSnapshot' for VMGroup 'AvamarBackup_<Hyper-V_Node_Name>-app-<#######>' 
winclustersvc DEBUG<0000>: ===> ValidateOutput  
winclustersvc DEBUG<0000>: WMI API return value is: '4096' 
winclustersvc DEBUG<0000>: Waiting for Job to complete... 
winclustersvc DEBUG<0000>: WMI job completed with status '10'  
winclustersvc WARN<0000>:  WMI API returned error: 'Failed to create checkpoint on collection 'AvamarBackup_<Hyper-V_Node_Name>-app-<#######>' (<GROUP_GUID>).
The operation failed.
Guest cluster validation on VM group 'AvamarBackup_<Hyper-V_Node_Name>-app-<#######>' (<GROUP_GUID>) failed for checkpoint creation.

Microsoft WMI API generates these messages when several VMs are selected from a specific Hyper-V Node in a backup Dataset.

The Hyper-V Node should have all recent Microsoft updates installed.

None of the VMs have disk set, shared disks, or in-guest CSV configured. It is not supported by Hyper-V Image backup.

Workaround:

• Use smaller groups. 
• Select fewer VMs from a specific Node in the backup Dataset.
• Open a case with Microsoft to address WMI API issue on Hyper-V Node.  

To enable debug in winclustersvc:

1. Use Notepad to create winclustersvc.cmd in C:\Program Files\avs\var\ folder on the Hyper-V Node - the owner of "EMC Avamar backup cluster client for <Avamar_clustered_client_name>"
2. Add --debug to it.
3. Restart "EMC Avamar Plug-in Service for Windows" on the Hyper-V Node. 
4. Rerun the backup to reproduce the issue.