The aircraft was maintained to AMM Chapters 4 and 5 of CESCOM, all maintenance was up to date and carried out by Approved Part 145 Organisations.
Prelim statement from AAIB indicated that there is no evidence to indicate an engine failure, nor indication of starter generator bearing failure which could cause engine vibration.
Any speculation regarding maintenance is purely that, speculation, so unless you have specific information regarding this aircraft which may be of value to the AAIB, best not muse on this on a public forum.
Best regards,
om15