An Item with the same key has already been added

Hello All,

I'm seeing a strange issue when trying to add a new-disk to a VM through powershell

I use the following commands:

Add-PSSnapin VMware.VimAutomation.Core

connect-viserver -server $MyVC

$server='MyServer'

$vm=get-vm $server

$NewDisk= New-HardDisk -VM $VM -CapacityGB $DiskSize -StorageFormat $StorageFormat

When I execute it, the disk gets added but the following is thrown into the output:

At line:1 char:11

+ $NewDisk= New-HardDisk -VM $VM -CapacityGB $DiskSize -StorageFormat $StorageForm ...

   ViCore.Cmdlets.Commands.VirtualDevice.NewHardDisk

When I rerun the command in the same powershell session then it gets executed without error.

Has anyone seen this behavior before?

Could this be a bug?

I've been looking for this error but this seems to be something very generic..

Many thanks in advance!

Filip