Debugging a race condition that only happens in a CI run is no joke.
Issue appears to be resolved.
Turned out to be a weird PowerShell thing. Basically had to pull a command from each module (Get-Command).. this allowed a completely unrelated command to do its thing with CIM.
I can only imagine that it was a quirk with how underlying runspaces work
In all fairness, this work has actually reminded me why I used to stan #powershell so much. Gripes aside you can actually get a lot done with very little.