Thanks Gem
So, if something has happened to disturb that carefully balanced system, then possibly there is oil leaking where there should not be oil; which is what seems to be reported. That leakage can lead to a fire, and a softened disk, which then maybe lets its blades go, and departs from the engine
Since we are speculating then posibly the why we are seeing the issue with the 972 and not the 970 is due to additional pressures or gas velocity due to the higher rated models effecting the balance.
Could be something that did not transfer over to the production turbine vs the prototype/test unit. There have been several mentions of the drain tubes plugging/coking over time which might decrease the ability to drain the oil away instead of being fuel to melt the disk when there is an improper balance.
Thanks again Gem
VFD