Rebooted the firewall and was able to delete the client.
It went into a non-responsive state via the GUI when attempting to delete it, forced a reboot via SSH and it came back up. Client was still there, hit delete again and this time it removed it.
It went into a non-responsive state via the GUI when attempting to delete it, forced a reboot via SSH and it came back up. Client was still there, hit delete again and this time it removed it.