The primary reason that the RB199 had so many problems was down to the fact that (due to cost of ownership) the RAF decided to send their HP Nozzle Guide Vanes for a wide gap braze repair by a repair agancy. the result was that they stopped buying new HPNGV's and repaired them instead.This disastrous as the HPNGV on RB199 was structural in that it transmitted all the structural loads through the aerofoil onto the outer platform which was then secured onto the casing. As a result, brazed HPNGV's had little structural rigidity and failed, allowing the HP inner static structure to move rearward contacting the HP rotor. As a result, two F3's crashed.
the MoD had to spend some £100m to fix such problems.