The problem is not just with QFIs though. Delayed or protracted training plus a shortage of frontline hours makes it difficult to find the experienced (ideally) third-tourists to fill QWI, QTI, QFI, TP, promotion cadre, exchange slots, SQEP for specialist roles etc.
The issues are exacerbated by a reduced number being pulled through to initial pension point since it was moved further away from the previous 38/16 point. Imposing restrictive RoS measures also pushes many to the door earlier than planned.
The aircrew cadre has not had a viable structure since the early 90s. Only the repeated cuts and manpower reductions have enabled the structure to survive. There simply isn't a plan in place to support steady-state aircrew manning.