The issue is that our Citrix environment uses a system called Provisioning Services (PVS). Here is a definition.
Provisioning Services streaming technology allows computers to be provisioned and re-provisioned in real time from a single shared-disk image. This enables administrators to completely eliminate the need to manage and patch individual systems. Instead, all image management is done on the master image.
Our Citrix Team has all Citrix servers scheduled to restart every night. When they restart they boot from the master image which basically reimages the server. This creates a new machine ID in Bigfix.
I think there is timing issue with the clientIdentityMatch parameter. It does not appear to be checking for an existing matching client prior to creating a new client.