Rolls Royce spitfire PRXIX PS853

You sound like an emergency medical hologram 😀

Suggest you look at a recent copy of Flypast that covered the BBMF and Arco, one of the engine issues that Roobarb mentioned pertaining to the modified engines is mentioned in that 🙂

What is the nature of the problem?

Engine problems with the converted Shack Griffons remain a problem dogging only the three aeroplanes fitted with them. There is hope on the horizon I understand.