We don't get as anal as NATS does about stuff that may have glitches.
I'm no great fan of NATS and the way they work but on this I support Gonzo completely.
If a controller is asked to use a piece of equipment to enable him or her to control and separate aeroplanes it should work reliably. The first time there is an incident because the equipment works incorrectly and misleads the controller the person who carries the can is the controller.
The people who put the controller into that position will always have an answer ... usually that the controller is the one with the licence and is responsible for not using any faulty equipment.