Just did some more tests, and the path for VMs that are in the root of the datacenter do not cause the problem.
Do you know for which VMs you get the error ?
And where these are located in the VMs and Templates view ?
Another possibility, are you running in multi mode ?
And are you connected to multiple vSphere servers ?
Do a
Get-PowerCLIConfiguration
to check. And if yes, display the open connections with
$global:defaultviservers