WojtekSz
The Supporting Structure of the Bearings and its shortcomings are well known, they are addressed by RR themselves, I believe. The IPT Case containing the IPT Disc and the LP/NGVs with Platform are supported by a center bore that is itself part of the Casing. These are ten Radial and hollow struts that are fastened to the Case with special fasteners (bolts). The AD does address the chronic loosening of these bolts, and requires their re-torquing at specific intervals. "Re-Torquing", "Borescoping", "Oil Inspections"; these are known "Palliatives". Palliative in the sense of treatment, not cure. The underlying consideration for the life of this powerplant is the rehabilitation back to profiles certified in its original certificate.
The squishy part is determining, and by whom, what constitutes Safety in pursuance of keeping this engine on wing. I can simply repeat that the cause of the chronic wear and shortened life of this machine is and was known. It is Vibration, and resonance; a "novelty" dependent on whom one asks. The core bores, bearings, and webs are subject to not additional stress, but normal stress that was unaddressed. It may be pedantic, but I think it is accurate. It is not a mystery, it never was. The engine landed on wing early, with insufficient test and a lurking problem that cannot be controlled given present design, not insofar as adherence to the certificate is involved. Decisions made about the future of the TRENT are forthcoming. Replacing moving mass every three hundred cycles may treat the disease, but it won't cure it.