The L1011 fan problem which resulted in fan blade release was due to a manufacturing process where 2 discs were cut from a single billet.
I first heard this over 40 years ago from a colleague who had previously worked in the RR department that keeps track of the history of every part used in every engine, from raw material onwards.
The failures were all in discs cut from one end of the billet. Those from the other end were fine. The problem went back to the production of the billet!