Sorry Findo but I didn't miss the original point just off topic a bit and responding to Wiley's plea - the procedures have had the sort of overhaul that Wiley wants.
On the real point of the thread - whether intermittent RT failure (or correct operation depending on your perspective) is a safety risk - there really is no argument. Of course it is.
I started to put a response to Monkey C's post together the other day when I read it but then realised he was just having a joke. He is, isn't he?
The simple fact is, in the busy terminal areas that NATS look after, clearances are not procedural and the system relies upon immediate, reliable and clear voice communications.