If there is only one duplicate, it can be fixed by removing one of the duplicates from the vCenter inventory.
Inventory Object can be checked via PowerCLi
Using PowerCLI
Download and install PowerCLI from PowerShell.
Run the commands below on one or all vCenters in linked mode to find the (vm-xxxx) MoRef ID you see in the error.
The process of finding the VM MoRef ID thru PowerCLI may have to be repeated multiple times depending on the number of times you see the error with different VM MoRef IDs while exporting the configuration data.
Here's an example :
Windows PowerShell
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PS C:\Users\User> Connect-VIServer 192.168.0.4
Name Port User
---- -- -- - ---
192.168.0.4 443 VSPHERE.LOCAL\Administrator
PS C:\Users\User> Get-VM | Sort-Object ID | ft -Property Name,ID -AutoSize
Name Id
---- --
App1 VirtualMachine-vm-123
Windows Template (35GB) VirtualMachine-vm-124
WebApp VirtualMachine-vm-1879
FileServ VirtualMachine-vm-1456