Thanks for your assistance Panos. The issue is now solved. It seems that if you enable WMI client probing on the policy enforcement firewalls (i.e. not the PAN200 which is being used as a UID agent) the probes do in fact take place. So it stands to reason that PANOS UID Agent does not carry out a WMI probe on behave of the policy enforcement firewalls. This behaviour is not very well documented.
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