Get-Ncsnapmirror command fails sometimes in powershell

Hi,

When SMSQL tries to get the snapvault relationship by invoking the command get-Ncsnapmirror it fails sometimes.

but the thing is the same command executed  successfully the other day in production.So not sure why it fails sometimes...

Can anyone help me out..?

Exception:

 General Critical Failed to run a command Get-NcSnapMirror.
Exception : Message : Command execution stopped because the preference variable "ErrorActionPreference" or common parameter is set to Stop: Object reference not set to an instance of an object.
Source : System.Management.Automation
StackTrace : at System.Management.Automation.Internal.PipelineProcessor.SynchronousExecuteEnumerate(Object input, Hashtable errorResults, Boolean enumerate)
at System.Management.Automation.Runspaces.LocalPipeline.InvokeHelper()
at System.Management.Automation.Runspaces.LocalPipeline.InvokeThreadProc() 

we are executing the command through >>pipeline.invoke(IEnumerable<>) method. 

Thanks.

Hemanth