I'm not too sure that the article you referenced is similar to what you are seeing.
The problem in the article is related to waiting for an async task.
And like the last entry in that article correctly states, a Task object does not refresh automatically.
Can you try your script, on a limited set of VMs, without the RunAsync switch?
And check if the error comes again for each VM.
It could also be useful to have a look in the vpxd log to find any additional information on why the error happens.